chore: Update SDK documentation (#4679)

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marvin-context-protocol[bot] 2026-08-06 19:56:40 -04:00 committed by GitHub
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@ -31,6 +31,28 @@
}
]
},
{
"group": "fastmcp.server",
"pages": [
"python-sdk/fastmcp-server-caching",
"python-sdk/fastmcp-server-completions",
"python-sdk/fastmcp-server-context",
"python-sdk/fastmcp-server-dependencies",
"python-sdk/fastmcp-server-elicitation",
"python-sdk/fastmcp-server-event_store",
"python-sdk/fastmcp-server-extensions",
"python-sdk/fastmcp-server-http",
"python-sdk/fastmcp-server-lifespan",
"python-sdk/fastmcp-server-low_level",
"python-sdk/fastmcp-server-mixins",
"python-sdk/fastmcp-server-providers",
"python-sdk/fastmcp-server-server",
"python-sdk/fastmcp-server-session_scoped_event_store",
"python-sdk/fastmcp-server-sessions",
"python-sdk/fastmcp-server-telemetry",
"python-sdk/fastmcp-server-transforms"
]
},
{
"group": "fastmcp.utilities",
"pages": [
@ -79,6 +101,7 @@
"python-sdk/fastmcp-utilities-mime",
"python-sdk/fastmcp-utilities-openapi",
"python-sdk/fastmcp-utilities-pagination",
"python-sdk/fastmcp-utilities-prefab",
"python-sdk/fastmcp-utilities-skills",
"python-sdk/fastmcp-utilities-tasks",
"python-sdk/fastmcp-utilities-tests",

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@ -35,7 +35,7 @@ Usage::
## Classes
### `FastMCPApp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L145" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `FastMCPApp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L149" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
A Provider that represents an MCP application.
@ -48,19 +48,19 @@ can find them by original name even when transforms have been applied.
**Methods:**
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L169" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L173" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
tool(self, name_or_fn: F) -> F
```
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L181" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L185" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
tool(self, name_or_fn: str | None = None) -> Callable[[F], F]
```
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L192" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L196" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
tool(self, name_or_fn: str | AnyFunction | None = None) -> Any
@ -83,19 +83,19 @@ Supports multiple calling patterns::
def save(name: str): ...
#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L259" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L266" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
ui(self, name_or_fn: F) -> F
```
#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L274" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L281" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
ui(self, name_or_fn: str | None = None) -> Callable[[F], F]
```
#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L288" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L295" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
ui(self, name_or_fn: str | AnyFunction | None = None) -> Any
@ -119,7 +119,7 @@ Supports multiple calling patterns::
def dashboard() -> Component: ...
#### `add_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L363" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `add_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L373" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_tool(self, tool: Tool | Callable[..., Any]) -> Tool
@ -130,13 +130,13 @@ Add a tool to this app programmatically.
The tool is tagged with this app's name for routing.
#### `lifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L419" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `lifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L432" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
lifespan(self) -> AsyncIterator[None]
```
#### `run` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L427" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `run` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/app.py#L440" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
run(self, transport: Literal['stdio', 'http', 'sse', 'streamable-http'] | None = None, **kwargs: Any) -> None

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@ -15,7 +15,7 @@ UI metadata for clients that support interactive app rendering.
## Functions
### `app_config_to_meta_dict` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L180" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `app_config_to_meta_dict` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L181" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
app_config_to_meta_dict(app: AppConfig | dict[str, Any]) -> dict[str, Any]
@ -25,9 +25,32 @@ app_config_to_meta_dict(app: AppConfig | dict[str, Any]) -> dict[str, Any]
Convert an AppConfig or dict to the wire-format dict for ``meta["ui"]``.
### `is_model_visible` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L188" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_model_visible(component: FastMCPComponent) -> bool
```
Whether a component may be shown to, or invoked by, the model.
Visibility is a declaration, and the MCP Apps spec puts the filtering on
the host — so ``tools/list`` carries app-only tools and the host keeps
them from the model. That division only works where a host stands between
the server and the model.
It does not hold for surfaces a server drives itself. A search result or
a code-mode catalog reaches the model as ordinary tool output, and a
call-tool proxy invokes on a name the model supplies; nothing downstream
can filter either. Those surfaces have to apply the declaration here.
A component with no ``visibility`` is visible: the field marks the
exception, and the spec's default is both audiences.
## Classes
### `ResourceCSP` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L20" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ResourceCSP` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L21" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Content Security Policy for MCP App resources.
@ -37,7 +60,7 @@ load resources from. Hosts use these declarations to build the
``Content-Security-Policy`` header for the sandboxed iframe.
### `ResourcePermissions` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L56" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ResourcePermissions` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L57" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Iframe sandbox permissions for MCP App resources.
@ -48,7 +71,7 @@ iframe. Hosts MAY honour these; apps should use JS feature detection
as a fallback.
### `AppConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L84" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `AppConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L85" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Configuration for MCP App tools and resources.
@ -63,7 +86,7 @@ values appear on the wire. Aliases match the MCP Apps wire format
(camelCase).
### `PrefabAppConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L124" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `PrefabAppConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L125" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
App configuration for Prefab tools with sensible defaults.
@ -83,7 +106,7 @@ Example::
**Methods:**
#### `model_post_init` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L140" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `model_post_init` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/apps/config.py#L141" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
model_post_init(self, __context: Any) -> None

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@ -10,7 +10,7 @@ Custom exceptions for FastMCP.
## Functions
### `to_mcp_error` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L122" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `to_mcp_error` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L117" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
to_mcp_error(exc: Exception) -> MCPError
@ -38,71 +38,61 @@ explicit code chosen upstream survives translation.
## Classes
### `FastMCPDeprecationWarning` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L34" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Deprecation warning for FastMCP APIs.
Subclass of DeprecationWarning so that standard warning filters
still apply, but FastMCP can selectively enable its own warnings
without affecting other libraries in the process.
### `FastMCPError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L43" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `FastMCPError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L38" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Base error for FastMCP.
### `ValidationError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L51" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ValidationError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L46" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Error in validating parameters or return values.
### `ResourceError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L55" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ResourceError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L50" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Error in resource operations.
### `ToolError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L59" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ToolError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L54" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Error in tool operations.
### `PromptError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L63" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `PromptError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L58" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Error in prompt operations.
### `InvalidSignature` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L67" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `InvalidSignature` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L62" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Invalid signature for use with FastMCP.
### `ClientError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L71" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ClientError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L66" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Error in client operations.
### `NotFoundError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L75" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `NotFoundError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L70" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Object not found.
### `DisabledError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L79" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `DisabledError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L74" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Object is disabled.
### `ResourceSecurityError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L83" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ResourceSecurityError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L78" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
A templated resource parameter failed path-security screening.
@ -114,13 +104,13 @@ for a resource that does not exist, and never reveals which parameter
or policy tripped.
### `AuthorizationError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L94" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `AuthorizationError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L89" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Error when authorization check fails.
### `InsufficientScopeError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L98" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `InsufficientScopeError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/exceptions.py#L93" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Authorization failed because the token is missing required OAuth scopes.

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@ -32,7 +32,7 @@ Example configuration:
## Functions
### `infer_transport_type_from_url` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L54" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `infer_transport_type_from_url` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L55" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
infer_transport_type_from_url(url: str | AnyUrl) -> Literal['http', 'sse']
@ -42,7 +42,7 @@ infer_transport_type_from_url(url: str | AnyUrl) -> Literal['http', 'sse']
Infer the appropriate transport type from the given URL.
### `update_config_file` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L373" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `update_config_file` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L376" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
update_config_file(file_path: Path, server_name: str, server_config: CanonicalMCPServerTypes) -> None
@ -57,7 +57,7 @@ worry about transforming server objects here.
## Classes
### `StdioMCPServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L179" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `StdioMCPServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L180" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
MCP server configuration for stdio transport.
@ -67,19 +67,19 @@ This is the canonical configuration format for MCP servers using stdio transport
**Methods:**
#### `to_transport` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L212" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `to_transport` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L213" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
to_transport(self) -> StdioTransport
to_transport(self) -> StdioTransport | FastMCPTransport
```
### `TransformingStdioMCPServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L224" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `TransformingStdioMCPServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L225" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
A Stdio server with tool transforms.
### `RemoteMCPServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L228" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `RemoteMCPServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L229" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
MCP server configuration for HTTP/SSE transport.
@ -89,19 +89,19 @@ This is the canonical configuration format for MCP servers using remote transpor
**Methods:**
#### `to_transport` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L264" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `to_transport` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L265" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
to_transport(self) -> StreamableHttpTransport | SSETransport
to_transport(self) -> StreamableHttpTransport | SSETransport | FastMCPTransport
```
### `TransformingRemoteMCPServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L291" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `TransformingRemoteMCPServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L294" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
A Remote server with tool transforms.
### `MCPConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L302" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `MCPConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L305" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
A configuration object for MCP Servers that conforms to the canonical MCP configuration format
@ -113,7 +113,7 @@ For an MCPConfig that is strictly canonical, see the `CanonicalMCPConfig` class.
**Methods:**
#### `wrap_servers_at_root` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L316" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `wrap_servers_at_root` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L319" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
wrap_servers_at_root(cls, values: dict[str, Any]) -> dict[str, Any]
@ -122,7 +122,7 @@ wrap_servers_at_root(cls, values: dict[str, Any]) -> dict[str, Any]
If there's no mcpServers key but there are server configs at root, wrap them.
#### `add_server` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L329" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `add_server` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L332" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_server(self, name: str, server: MCPServerTypes) -> None
@ -131,7 +131,7 @@ add_server(self, name: str, server: MCPServerTypes) -> None
Add or update a server in the configuration.
#### `from_dict` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L334" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `from_dict` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L337" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
from_dict(cls, config: dict[str, Any]) -> Self
@ -140,7 +140,7 @@ from_dict(cls, config: dict[str, Any]) -> Self
Parse MCP configuration from dictionary format.
#### `to_dict` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L338" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `to_dict` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L341" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
to_dict(self) -> dict[str, Any]
@ -149,7 +149,7 @@ to_dict(self) -> dict[str, Any]
Convert MCPConfig to dictionary format, preserving all fields.
#### `write_to_file` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L342" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `write_to_file` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L345" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
write_to_file(self, file_path: Path) -> None
@ -158,7 +158,7 @@ write_to_file(self, file_path: Path) -> None
Write configuration to JSON file.
#### `from_file` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L348" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `from_file` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L351" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
from_file(cls, file_path: Path) -> Self
@ -167,7 +167,7 @@ from_file(cls, file_path: Path) -> Self
Load configuration from JSON file.
### `CanonicalMCPConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L358" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `CanonicalMCPConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L361" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Canonical MCP configuration format.
@ -178,7 +178,7 @@ The format is designed to be client-agnostic and extensible for future use cases
**Methods:**
#### `add_server` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L368" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `add_server` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/mcp_config.py#L371" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_server(self, name: str, server: CanonicalMCPServerTypes) -> None

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@ -0,0 +1,48 @@
---
title: caching
sidebarTitle: caching
---
# `fastmcp.server.caching`
Server-level cache hints for FastMCP (SEP-2549).
A FastMCP server opts every SDK-cacheable result it emits into client-side
caching by setting `cache_ttl` (seconds) and, optionally, `cache_scope` on the
`FastMCP` constructor. The hint is uniform by construction: one server-level
value applies to `tools/list`, `prompts/list`, `resources/list`,
`resources/templates/list`, `resources/read`, and `server/discover` alike — no
per-component surface and no aggregation.
FastMCP does not hand-set the wire fields. It passes the hint through to the SDK
low-level `Server(cache_hints=...)`, whose runner fills `ttlMs`/`cacheScope` on
every cacheable result via `apply_cache_hint`, leaving any field a handler set
explicitly untouched. Honoring is modern-only and opt-in on the client: a hinted
server is inert unless the client passes `cache=` and negotiates `2026-07-28`.
## Functions
### `build_cache_hints` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/caching.py#L29" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
build_cache_hints(cache_ttl: int | None, cache_scope: CacheScope | None) -> dict[CacheableMethod, CacheHint] | None
```
Build the per-method `CacheHint` map for the SDK low-level server.
`cache_ttl` is in seconds and is converted to the wire's milliseconds. When
`cache_ttl` is `None` the server emits no hint, so its wire output is
identical to a server that never set one; a `cache_scope` given without a
`cache_ttl` is meaningless (the client gates caching on the presence of a
TTL) and is rejected rather than silently ignored.
Returns `None` when no hint is set, or a map applying the same hint to every
SDK-cacheable method otherwise.
**Raises:**
- `ValueError`: If `cache_ttl` is not positive, or if `cache_scope` is set
without `cache_ttl`.

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@ -0,0 +1,41 @@
---
title: completions
sidebarTitle: completions
---
# `fastmcp.server.completions`
Server-side argument completion for FastMCP.
A completion request names a reference — a specific prompt or resource
template — and the argument being completed, plus a context of the argument
values already supplied. The server answers with candidate string values.
FastMCP surfaces this as a single server-level handler registered with
``@mcp.completion``, mirroring the MCP SDK's own ``completion/complete`` shape
and FastMCP's client-side ``Client.complete()``. The handler receives the
reference, the argument, and the optional context, and returns candidates for
whichever reference/argument pair it recognizes.
## Functions
### `normalize_completion` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/completions.py#L54" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
normalize_completion(result: CompletionValues) -> mcp_types.Completion
```
Coerce a handler's return value into a wire ``Completion``.
A returned ``str`` is rejected: it is almost always a mistake (the value
would iterate into one-character candidates), so it raises rather than
silently producing surprising output.
The MCP contract caps a completion at 100 values, so a longer result is
truncated to the first 100 with ``has_more`` set — a handler that returns
thousands of matches emits a conforming response rather than an oversized
one that strict clients reject.

View file

@ -0,0 +1,711 @@
---
title: context
sidebarTitle: context
---
# `fastmcp.server.context`
## Functions
### `set_transport` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L97" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_transport(transport: TransportType) -> Token[TransportType | None]
```
Set the current transport type. Returns token for reset.
### `reset_transport` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L104" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
reset_transport(token: Token[TransportType | None]) -> None
```
Reset transport to previous value.
### `set_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L134" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_context(context: Context) -> Generator[Context, None, None]
```
## Classes
### `LogData` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L110" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Data object for passing log arguments to client-side handlers.
This provides an interface to match the Python standard library logging,
for compatibility with structured logging.
### `Context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L143" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Context object providing access to MCP capabilities.
This provides a cleaner interface to MCP's RequestContext functionality.
It gets injected into tool and resource functions that request it via type hints.
To use context in a tool function, add a parameter with the Context type annotation:
```python
@server.tool
async def my_tool(x: int, ctx: Context) -> str:
# Log messages to the client
await ctx.info(f"Processing {x}")
await ctx.debug("Debug info")
await ctx.warning("Warning message")
await ctx.error("Error message")
# Report progress
await ctx.report_progress(50, 100, "Processing")
# Access resources
data = await ctx.read_resource("resource://data")
# Get request info
request_id = ctx.request_id
client_id = ctx.client_id
# Manage state across the session (persists across requests)
await ctx.set_state("key", "value")
value = await ctx.get_state("key")
# Store non-serializable values for the current request only
await ctx.set_state("client", http_client, serializable=False)
return str(x)
```
State Management:
Context provides session-scoped state that persists across requests within
the same MCP session. State is automatically keyed by session, ensuring
isolation between different clients.
State set during `on_initialize` middleware will persist to subsequent tool
calls when using the same session object (STDIO, SSE, single-server HTTP).
For distributed/serverless HTTP deployments where different machines handle
the init and tool calls, state is isolated by the mcp-session-id header.
The context parameter name can be anything as long as it's annotated with Context.
The context is optional - tools that don't need it can omit the parameter.
**Methods:**
#### `is_background_task` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L224" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_background_task(self) -> bool
```
True when this context is running in a background task (Docket worker).
When True, certain operations like elicit() will use task-aware
implementations that can pause the task and wait for client input.
#### `task_id` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L242" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
task_id(self) -> str | None
```
Get the background task ID if running in a background task.
Returns None if not running in a background task context.
#### `origin_request_id` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L250" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
origin_request_id(self) -> str | None
```
Get the request ID that originated this execution, if available.
In foreground request mode, this is the current request_id.
In background task mode, this is the request_id captured when the task
was submitted, if one was available.
#### `fastmcp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L262" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
fastmcp(self) -> FastMCP
```
Get the FastMCP instance.
#### `request_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L312" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
request_context(self) -> FastMCPRequestContext | None
```
Access to the underlying request context.
Returns None when the MCP session has not been established yet.
Returns the FastMCPRequestContext wrapper once the MCP session is available.
For HTTP request access in middleware, use `get_http_request()` from fastmcp.server.dependencies,
which works whether or not the MCP session is available.
Example in middleware:
```python
async def on_request(self, context, call_next):
ctx = context.fastmcp_context
if ctx.request_context:
# MCP session available - can access session_id, request_id, etc.
session_id = ctx.session_id
else:
# MCP session not available yet - use HTTP helpers
from fastmcp.server.dependencies import get_http_request
request = get_http_request()
return await call_next(context)
```
#### `client_extension_settings` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L337" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
client_extension_settings(self, identifier: str) -> dict[str, Any] | None
```
This request's per-request opt-in settings for an MCP extension.
SEP-2133 extensions negotiate per request: the client repeats its
extension capabilities in each request's ``_meta`` under
``io.modelcontextprotocol/clientCapabilities`` → ``extensions`` →
``identifier``. Returns the declared settings dict (possibly empty) when
the extension was opted in for this request, or ``None`` when it was
not (or there is no active request). This bridges an extension's
``tools/call`` interceptor — which receives a FastMCP ``Context`` — to
the request's declared client capabilities.
#### `input_responses` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L378" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
input_responses(self) -> mcp_types.InputResponses | None
```
Client responses to a prior `InputRequiredResult.input_requests`.
The multi-round-trip guard channel (SEP-2322). A guard tool inspects
this to decide what to do on each round: `None` on the initial round
(nothing has been asked yet, or the client retried without responses),
so the tool returns an `InputRequiredResult` to ask; present on a later
round, so the tool reads the answers and proceeds. It is a mapping whose
keys match the `input_requests` map the tool minted; each value is the
client's result for that request (an `ElicitResult`, `CreateMessageResult`,
or `ListRootsResult`).
In a background task there is no wire request, so this falls back to the
responses the in-task guard loop delivered (see the tasks extension).
#### `request_state` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L399" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
request_state(self) -> str | None
```
Opaque state echoed from a prior `InputRequiredResult.request_state`.
The multi-round-trip guard channel (SEP-2322): whatever a tool put in
`InputRequiredResult.request_state` on an earlier round is handed back
here (as plaintext — the framework seals it on the wire and unseals it
before the tool runs, so tampering is rejected before this is read).
`None` on the initial round. Use it to carry a small amount of computed
state across rounds without re-deriving it.
In a background task there is no wire request, so this falls back to the
state the in-task guard loop re-injected (see the tasks extension).
#### `lifespan_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L418" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
lifespan_context(self) -> dict[str, Any]
```
Access the server's lifespan context.
Returns the context dict yielded by *this* server's lifespan function.
For a mounted child this is the child's own lifespan, not the parent's
— the MCP session always belongs to the parent, so reading from the
request context would return the parent's. We read directly from the
server's cached lifespan result instead, which is set by the
per-server ``_lifespan_manager`` regardless of mount position.
Returns an empty dict if no lifespan was configured.
Example:
```python
@server.tool
def my_tool(ctx: Context) -> str:
db = ctx.lifespan_context.get("db")
if db:
return db.query("SELECT 1")
return "No database connection"
```
#### `report_progress` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L453" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
report_progress(self, progress: float, total: float | None = None, message: str | None = None) -> None
```
Report progress for the current operation.
Works in both foreground (MCP progress notifications) and background
(Docket task execution) contexts.
**Args:**
- `progress`: Current progress value e.g. 24
- `total`: Optional total value e.g. 100
- `message`: Optional status message describing current progress
#### `list_resources` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L552" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_resources(self) -> list[SDKResource]
```
List all available resources from the server.
**Returns:**
- List of Resource objects available on the server
#### `list_prompts` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L563" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_prompts(self) -> list[SDKPrompt]
```
List all available prompts from the server.
**Returns:**
- List of Prompt objects available on the server
#### `get_prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L574" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_prompt(self, name: str, arguments: dict[str, Any] | None = None) -> GetPromptResult
```
Get a prompt by name with optional arguments.
**Args:**
- `name`: The name of the prompt to get
- `arguments`: Optional arguments to pass to the prompt
**Returns:**
- The prompt result
#### `read_resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L593" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
read_resource(self, uri: str | AnyUrl) -> ResourceResult
```
Read a resource by URI.
**Args:**
- `uri`: Resource URI to read
**Returns:**
- ResourceResult with contents
#### `log` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L609" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
log(self, message: str, level: LoggingLevel | None = None, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
```
Send a log message to the client.
Messages sent to Clients are also logged to the `fastmcp.server.context.to_client` logger with a level of `DEBUG`.
**Args:**
- `message`: Log message
- `level`: Optional log level. One of "debug", "info", "notice", "warning", "error", "critical",
"alert", or "emergency". Default is "info".
- `logger_name`: Optional logger name
- `extra`: Optional mapping for additional arguments
#### `transport` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L650" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
transport(self) -> TransportType | None
```
Get the current transport type.
Returns the transport type used to run this server: "stdio", "sse",
or "streamable-http". Returns None if called outside of a server context.
#### `client_supports_extension` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L658" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
client_supports_extension(self, extension_id: str) -> bool
```
Check whether the connected client supports a given MCP extension.
Inspects the ``extensions`` extra field on ``ClientCapabilities``
sent by the client during initialization.
Reads the client's advertised capabilities from the session, which is
available in request mode and in background-task mode (where the
snapshot session preserves the client's initialize params). Returns
``False`` when no session is available (e.g., a distributed worker with
no live session, or outside any context) or when the client did not
advertise the extension.
Example::
from fastmcp.apps.config import UI_EXTENSION_ID
@mcp.tool
async def my_tool(ctx: Context) -> str:
if ctx.client_supports_extension(UI_EXTENSION_ID):
return "UI-capable client"
return "text-only client"
#### `client_id` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L688" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
client_id(self) -> str | None
```
Get the client ID if available.
#### `request_id` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L696" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
request_id(self) -> str
```
Get the unique ID for this request.
Raises RuntimeError if MCP request context is not available.
#### `session_id` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L709" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
session_id(self) -> str
```
Get the MCP session ID for ALL transports.
Returns the session ID that can be used as a key for session-based
data storage (e.g., Redis) to share data between tool calls within
the same client session.
**Returns:**
- The session ID for StreamableHTTP transports, or a generated ID
- for other transports.
#### `session` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L794" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
session(self) -> ServerSession
```
Access to the underlying session for advanced usage.
In request mode: Returns the session from the active request context.
In background task mode: Returns the session stored at Context creation.
Raises RuntimeError if no session is available.
#### `debug` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L820" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
debug(self, message: str, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
```
Send a `DEBUG`-level message to the connected MCP Client.
Messages sent to Clients are also logged to the `fastmcp.server.context.to_client` logger with a level of `DEBUG`.
#### `info` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L836" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
info(self, message: str, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
```
Send a `INFO`-level message to the connected MCP Client.
Messages sent to Clients are also logged to the `fastmcp.server.context.to_client` logger with a level of `DEBUG`.
#### `warning` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L852" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
warning(self, message: str, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
```
Send a `WARNING`-level message to the connected MCP Client.
Messages sent to Clients are also logged to the `fastmcp.server.context.to_client` logger with a level of `DEBUG`.
#### `error` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L868" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
error(self, message: str, logger_name: str | None = None, extra: Mapping[str, Any] | None = None) -> None
```
Send a `ERROR`-level message to the connected MCP Client.
Messages sent to Clients are also logged to the `fastmcp.server.context.to_client` logger with a level of `DEBUG`.
#### `send_notification` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L884" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
send_notification(self, notification: mcp_types.ServerNotification) -> None
```
Send a notification to the client immediately.
**Args:**
- `notification`: An MCP notification instance (e.g., ToolListChangedNotification())
#### `close_sse_stream` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L904" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
close_sse_stream(self) -> None
```
Close the current response stream to trigger client reconnection.
When using StreamableHTTP transport with an EventStore configured, this
method gracefully closes the HTTP connection for the current request.
The client will automatically reconnect (after `retry_interval` milliseconds)
and resume receiving events from where it left off via the EventStore.
This is useful for long-running operations to avoid load balancer timeouts.
Instead of holding a connection open for minutes, you can periodically close
and let the client reconnect.
#### `elicit` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L958" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
elicit(self, message: str, response_type: type[T]) -> AcceptedElicitation[T] | DeclinedElicitation | CancelledElicitation
```
The accepted elicitation will contain the response data
#### `elicit` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L969" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
elicit(self, message: str, response_type: list[str]) -> AcceptedElicitation[str] | DeclinedElicitation | CancelledElicitation
```
When response_type is a list of strings, the accepted elicitation will
contain the selected string response
#### `elicit` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L981" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
elicit(self, message: str, response_type: dict[str, dict[str, str]]) -> AcceptedElicitation[str] | DeclinedElicitation | CancelledElicitation
```
When response_type is a dict mapping keys to title dicts, the accepted
elicitation will contain the selected key
#### `elicit` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L993" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
elicit(self, message: str, response_type: list[list[str]]) -> AcceptedElicitation[list[str]] | DeclinedElicitation | CancelledElicitation
```
When response_type is a list containing a list of strings (multi-select),
the accepted elicitation will contain a list of selected strings
#### `elicit` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L1005" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
elicit(self, message: str, response_type: list[dict[str, dict[str, str]]]) -> AcceptedElicitation[list[str]] | DeclinedElicitation | CancelledElicitation
```
When response_type is a list containing a dict mapping keys to title dicts
(multi-select with titles), the accepted elicitation will contain a list of
selected keys
#### `elicit` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L1017" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
elicit(self, message: str, response_type: type[T] | list[str] | dict[str, dict[str, str]] | list[list[str]] | list[dict[str, dict[str, str]]]) -> AcceptedElicitation[T] | AcceptedElicitation[dict[str, Any]] | AcceptedElicitation[str] | AcceptedElicitation[list[str]] | DeclinedElicitation | CancelledElicitation
```
Send an elicitation request to the client and await the response.
Call this method at any time to request additional information from
the user through the client. The client must support elicitation,
or the request will error.
Note that the MCP protocol only supports simple object schemas with
primitive types. You can provide a dataclass, TypedDict, or BaseModel to
comply. If you provide a primitive type, an object schema with a single
"value" field will be generated for the MCP interaction and
automatically deconstructed into the primitive type upon response.
``response_type`` is required. Pass ``bool`` when all you need is a
confirmation; an empty schema leaves some clients rendering an empty,
non-functional form.
**Args:**
- `message`: A human-readable message explaining what information is needed
- `response_type`: The type of the response, which should be a primitive
type or dataclass or BaseModel. If it is a primitive type, an
object schema with a single "value" field will be generated.
- `response_title`: Optional label to display for the wrapped ``value``
field when ``response_type`` is a scalar, Literal, Enum, or one
of the dict/list shorthand forms. Overrides the auto-generated
"Value" label. Raises ``TypeError`` if passed with a BaseModel,
dataclass, or ``None`` response type (use ``Field(title=...)``
on the model instead).
- `response_description`: Optional description to attach to the wrapped
``value`` field. Same scope rules as ``response_title``.
#### `set_state` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L1110" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_state(self, key: str, value: Any) -> None
```
Set a value in the state store.
By default, values are stored in the session-scoped state store and
persist across requests within the same MCP session. Values must be
JSON-serializable (dicts, lists, strings, numbers, etc.).
For non-serializable values (e.g., HTTP clients, database connections),
pass ``serializable=False``. These values are stored in a request-scoped
dict and only live for the current MCP request (tool call, resource
read, or prompt render). They will not be available in subsequent
requests.
The key is automatically prefixed with the session identifier.
#### `get_state` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L1164" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_state(self, key: str) -> Any
```
Get a value from the state store.
Checks request-scoped state first (set with ``serializable=False``),
then falls back to the session-scoped state store.
Returns None if the key is not found.
#### `delete_state` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L1178" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
delete_state(self, key: str) -> None
```
Delete a value from the state store.
Removes from both request-scoped and session-scoped stores.
#### `enable_components` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L1199" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
enable_components(self) -> None
```
Enable components matching criteria for this session only.
Session rules override global transforms. Rules accumulate - each call
adds a new rule to the session. Later marks override earlier ones
(Visibility transform semantics).
Sends notifications to this session only: ToolListChangedNotification,
ResourceListChangedNotification, and PromptListChangedNotification.
**Args:**
- `names`: Component names or URIs to match.
- `keys`: Component keys to match (e.g., {"tool\:my_tool@v1"}).
- `version`: Component version spec to match.
- `tags`: Tags to match (component must have at least one).
- `components`: Component types to match (e.g., {"tool", "prompt"}).
- `match_all`: If True, matches all components regardless of other criteria.
#### `disable_components` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L1237" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
disable_components(self) -> None
```
Disable components matching criteria for this session only.
Session rules override global transforms. Rules accumulate - each call
adds a new rule to the session. Later marks override earlier ones
(Visibility transform semantics).
Sends notifications to this session only: ToolListChangedNotification,
ResourceListChangedNotification, and PromptListChangedNotification.
**Args:**
- `names`: Component names or URIs to match.
- `keys`: Component keys to match (e.g., {"tool\:my_tool@v1"}).
- `version`: Component version spec to match.
- `tags`: Tags to match (component must have at least one).
- `components`: Component types to match (e.g., {"tool", "prompt"}).
- `match_all`: If True, matches all components regardless of other criteria.
#### `reset_visibility` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/context.py#L1275" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
reset_visibility(self) -> None
```
Clear all session visibility rules.
Use this to reset session visibility back to global defaults.
Sends notifications to this session only: ToolListChangedNotification,
ResourceListChangedNotification, and PromptListChangedNotification.

View file

@ -0,0 +1,614 @@
---
title: dependencies
sidebarTitle: dependencies
---
# `fastmcp.server.dependencies`
Dependency injection for FastMCP.
DI features (Depends, CurrentContext, CurrentFastMCP) work without pydocket
using the uncalled-for DI engine. The docket-specific dependencies
(``CurrentDocket``, ``CurrentWorker``) and background task execution live in the
``fastmcp-tasks`` package.
## Functions
### `bind_request_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L104" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
bind_request_context(ctx: ServerRequestContext) -> Generator[FastMCPRequestContext, None, None]
```
Bind a ``FastMCPRequestContext`` for the duration of a handler.
Constructs the wrapper from the SDK's per-request context and sets/resets
the ``fastmcp_request_ctx`` ContextVar. Every request adapter and the
initialize middleware enters this so ``Context`` and dependency helpers can
read the active request from the ContextVar.
### `extract_version_spec` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L131" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
extract_version_spec(meta: dict[str, Any] | None) -> str | None
```
Extract the FastMCP component version from a lifted ``_meta`` block.
### `set_background_context_factory` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L185" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_background_context_factory(factory: Callable[[], Awaitable[Context | None]] | None) -> None
```
Install (or clear) the background-task ``Context`` factory.
The factory returns an already-entered ``Context`` (so ``_current_context``
is set for cleanup) when called inside a worker, or ``None`` when there is
no task context. Passing ``None`` restores core's no-worker-fallback
behavior.
### `set_worker_server_resolver` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L207" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_worker_server_resolver(resolver: Callable[[], FastMCP | None] | None) -> None
```
Install (or clear) the worker-server resolver used by ``get_server()``.
### `is_docket_available` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L244" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_docket_available() -> bool
```
Check if a compatible pydocket (>= 0.19.0) is installed and importable.
Three things have to be true for fastmcp's task features to work:
1. pydocket distribution metadata is discoverable
2. its version is at least ``_MIN_DOCKET_VERSION`` (older versions are
missing symbols like ``docket.dependencies.current_execution``,
which fastmcp imports on the request hot path)
3. the package actually imports — guards against broken/partial
installs where metadata exists but ``import docket`` blows up
Any of those failing means we treat docket as unavailable and fall back
to the no-tasks code paths instead of crashing deep inside a request.
### `transform_context_annotations` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L276" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
transform_context_annotations(fn: Callable[..., Any]) -> Callable[..., Any]
```
Transform injected-by-type params into Dependency-defaulted params.
Transforms ALL params typed as Context (into ``= CurrentContext()``) and as
UserSession (into ``= CurrentSession()``) to use Docket's DI system, unless
they already have a Dependency-based default.
This unifies the legacy type annotation DI with Docket's Depends() system,
allowing both patterns to work through a single resolution path.
Note: Only POSITIONAL_OR_KEYWORD parameters are reordered (params with defaults
after those without). KEYWORD_ONLY parameters keep their position since Python
allows them to have defaults in any order.
**Args:**
- `fn`: Function to transform
**Returns:**
- Function with modified signature (same function object, updated __signature__)
### `get_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L442" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_context() -> Context
```
Get the current FastMCP Context instance directly.
### `get_server` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L452" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_server() -> FastMCP
```
Get the current FastMCP server instance directly.
In a background-task worker the tasks extension's resolver is consulted
first, so a mounted-child task resolves to the child server rather than the
root that started the worker (#3571).
**Returns:**
- The active FastMCP server
**Raises:**
- `RuntimeError`: If no server in context
### `get_session` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L480" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_session(session_id: str) -> Session
```
Resolve and validate a `Session` for an explicit `session_id`.
Pair with a `session_id: SessionId` tool argument (the agent obtains an id
from `create_session` and passes it back). For a single per-user bucket with
nothing for the agent to pass, inject `session: UserSession` instead.
State is keyed by `(principal, session_id)`: the authenticated principal is
the isolation wall and `session_id` organizes sessions within it. The id must
have been minted by `create_session` under the current principal; an id that
was never created, or created under a different principal, raises
`InvalidSession` rather than resolving to a fresh empty bucket (the specific
reason is logged at debug level, never returned to the caller).
Like `get_server()`, this resolves through the task-aware server, so it needs
no foreground context — it works from a `task=True` tool's Docket worker as
well as a normal request.
### `get_http_request` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L515" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_http_request() -> Request
```
Get the current HTTP request.
Tries MCP SDK's request_ctx first, then falls back to FastMCP's HTTP context.
### `get_http_headers` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L536" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_http_headers(include_all: bool = False, include: set[str] | None = None) -> dict[str, str]
```
Extract headers from the current HTTP request if available.
Never raises an exception, even if there is no active HTTP request (in which case
an empty dict is returned).
By default, strips problematic headers like `content-length` and `authorization`
that cause issues if forwarded to downstream services. If `include_all` is True,
all headers are returned.
The `include` parameter allows specific headers to be included even if they would
normally be excluded. This is useful for proxy transports that need to forward
authorization headers to upstream MCP servers.
### `get_access_token` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L600" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_access_token() -> AccessToken | None
```
Get the FastMCP access token from the current context.
This function first tries to get the token from the current HTTP request's scope,
which is more reliable for long-lived connections where the SDK's auth_context_var
may become stale after token refresh. Falls back to the SDK's context var if no
request is available.
**Returns:**
- The access token if an authenticated user is available, None otherwise.
### `without_injected_parameters` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L659" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
without_injected_parameters(fn: Callable[..., Any]) -> Callable[..., Any]
```
Create a wrapper function without injected parameters.
Returns a wrapper that excludes Context and Docket dependency parameters,
making it safe to use with Pydantic TypeAdapter for schema generation and
validation. The wrapper internally handles all dependency resolution and
Context injection when called.
Handles:
- Legacy Context injection (always works)
- Depends() injection (always works - uses docket or vendored DI engine)
**Args:**
- `fn`: Original function with Context and/or dependencies
- `run_in_thread`: For sync ``fn``, whether to dispatch the call to a worker
thread after resolving dependencies. Defaults to True. Set to False
to call ``fn`` inline on the event loop thread — required for
thread-affinity libraries (e.g. Windows COM). Ignored for async fns.
**Returns:**
- Async wrapper function without injected parameters
### `resolve_dependencies` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L820" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
resolve_dependencies(fn: Callable[..., Any], arguments: dict[str, Any]) -> AsyncGenerator[dict[str, Any], None]
```
Resolve dependencies for a FastMCP function.
This function:
1. Filters out any dependency parameter names from user arguments (security)
2. Resolves Depends() parameters via the DI system
The filtering prevents external callers from overriding injected parameters by
providing values for dependency parameter names. This is a security feature.
Note: Context injection is handled via transform_context_annotations() which
converts `ctx: Context` to `ctx: Context = Depends(get_context)` at registration
time, so all injection goes through the unified DI system.
**Args:**
- `fn`: The function to resolve dependencies for
- `arguments`: User arguments (may contain keys that match dependency names,
which will be filtered out)
### `CurrentContext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L945" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
CurrentContext() -> Context
```
Get the current FastMCP Context instance.
This dependency provides access to the active FastMCP Context for the
current MCP operation (tool/resource/prompt call).
**Returns:**
- A dependency that resolves to the active Context instance
**Raises:**
- `RuntimeError`: If no active context found (during resolution)
### `OptionalCurrentContext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L970" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
OptionalCurrentContext() -> Context | None
```
Get the current FastMCP Context, or None when no context is active.
### `CurrentFastMCP` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L990" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
CurrentFastMCP() -> FastMCP
```
Get the current FastMCP server instance.
This dependency provides access to the active FastMCP server.
**Returns:**
- A dependency that resolves to the active FastMCP server
**Raises:**
- `RuntimeError`: If no server in context (during resolution)
### `CurrentRequest` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1030" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
CurrentRequest() -> Request
```
Get the current HTTP request.
This dependency provides access to the Starlette Request object for the
current HTTP request. Only available when running over HTTP transports
(SSE or Streamable HTTP).
**Returns:**
- A dependency that resolves to the active Starlette Request
**Raises:**
- `RuntimeError`: If no HTTP request in context (e.g., STDIO transport)
### `CurrentHeaders` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1071" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
CurrentHeaders() -> dict[str, str]
```
Get the current HTTP request headers.
This dependency provides access to the HTTP headers for the current request,
including the authorization header. Returns an empty dictionary when no HTTP
request is available, making it safe to use in code that might run over any
transport.
**Returns:**
- A dependency that resolves to a dictionary of header name -> value
### `CurrentAccessToken` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1289" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
CurrentAccessToken() -> AccessToken
```
Get the current access token for the authenticated user.
This dependency provides access to the AccessToken for the current
authenticated request. Raises an error if no authentication is present.
**Returns:**
- A dependency that resolves to the active AccessToken
**Raises:**
- `RuntimeError`: If no authenticated user (use get_access_token() for optional)
### `TokenClaim` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1346" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
TokenClaim(name: str) -> str
```
Get a specific claim from the access token.
This dependency extracts a single claim value from the current access token.
It's useful for getting user identifiers, roles, or other token claims
without needing the full token object.
**Args:**
- `name`: The name of the claim to extract (e.g., "oid", "sub", "email")
**Returns:**
- A dependency that resolves to the claim value as a string
**Raises:**
- `RuntimeError`: If no access token is available or claim is missing
## Classes
### `FastMCPRequestContext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L55" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
FastMCP-owned wrapper around the SDK's per-request context.
The SDK v2 runner hands each handler a fresh ``ServerRequestContext`` as an
argument rather than exposing it through a ContextVar. FastMCP owns this
ContextVar (``fastmcp_request_ctx``) and each request adapter binds a
``FastMCPRequestContext`` at the top of the handler (and the initialize
middleware binds it too).
A wrapper rather than the raw context because the SDK's
``ServerRequestContext.meta`` is a bare ``RequestParamsMeta`` TypedDict that
only carries ``progress_token`` — it does not carry ``_meta.fastmcp`` or the
distributed-trace parent. Those live in the raw params dict under ``_meta``,
which this wrapper lifts once so downstream consumers have a stable surface.
### `ProgressLike` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1099" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Protocol for progress tracking interface.
Defines the common interface between InMemoryProgress (server context)
and Docket's Progress (worker context).
**Methods:**
#### `current` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1107" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
current(self) -> int | None
```
Current progress value.
#### `total` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1112" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
total(self) -> int
```
Total/target progress value.
#### `message` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1117" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
message(self) -> str | None
```
Current progress message.
#### `set_total` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1121" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_total(self, total: int) -> None
```
Set the total/target value for progress tracking.
#### `increment` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1125" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
increment(self, amount: int = 1) -> None
```
Atomically increment the current progress value.
#### `set_message` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1129" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_message(self, message: str | None) -> None
```
Update the progress status message.
### `InMemoryProgress` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1134" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
In-memory progress tracker for immediate tool execution.
Provides the same interface as Docket's Progress but stores state in memory
instead of Redis. Useful for testing and immediate execution where
progress doesn't need to be observable across processes.
**Methods:**
#### `current` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1159" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
current(self) -> int | None
```
#### `total` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1163" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
total(self) -> int
```
#### `message` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1167" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
message(self) -> str | None
```
#### `set_total` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1170" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_total(self, total: int) -> None
```
Set the total/target value for progress tracking.
#### `increment` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1176" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
increment(self, amount: int = 1) -> None
```
Atomically increment the current progress value.
#### `set_message` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1185" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_message(self, message: str | None) -> None
```
Update the progress status message.
### `Progress` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1190" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Progress dependency that works in both server and worker contexts.
In a Docket worker, delegates to the execution's Redis-backed progress
(observable across processes). Otherwise, uses in-memory tracking.
The shared default instance acts as a stateless factory — ``__aenter__``
creates a fresh ``Progress`` per invocation so concurrent tasks never
share mutable state.
**Methods:**
#### `current` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1231" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
current(self) -> int | None
```
Current progress value.
#### `total` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1237" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
total(self) -> int
```
Total/target progress value.
#### `message` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1243" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
message(self) -> str | None
```
Current progress message.
#### `set_total` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1248" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_total(self, total: int) -> None
```
Set the total/target value for progress tracking.
#### `increment` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1253" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
increment(self, amount: int = 1) -> None
```
Atomically increment the current progress value.
#### `set_message` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/dependencies.py#L1258" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_message(self, message: str | None) -> None
```
Update the progress status message.

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---
title: elicitation
sidebarTitle: elicitation
---
# `fastmcp.server.elicitation`
## Functions
### `parse_elicit_response_type` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L143" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
parse_elicit_response_type(response_type: Any, response_title: str | None = None, response_description: str | None = None) -> ElicitConfig
```
Parse response_type into schema and handling configuration.
A response type is required; ``None`` raises ``TypeError``. Supports
multiple syntaxes:
- dict: `{"low": {"title": "..."}}` -> single-select titled enum
- list patterns:
- `[["a", "b"]]` -> multi-select untitled
- `[{"low": {...}}]` -> multi-select titled
- `["a", "b"]` -> single-select untitled
- `list\[X]` type annotation: multi-select with type
- Scalar types (bool, int, float, str, Literal, Enum): single value
- Other types (dataclass, BaseModel): use directly
The ``response_title`` and ``response_description`` arguments customize the
label and description of the wrapped ``value`` property for the scalar/dict/list
shorthand forms. They are only valid when FastMCP is wrapping the response
type; passing them with a full BaseModel/dataclass raises ``TypeError``,
because in those cases the user already controls field metadata via
``Field(title=..., description=...)``.
### `handle_elicit_accept` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L310" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
handle_elicit_accept(config: ElicitConfig, content: Any) -> AcceptedElicitation[Any]
```
Handle an accepted elicitation response.
**Args:**
- `config`: The elicitation configuration from parse_elicit_response_type
- `content`: The response content from the client
**Returns:**
- AcceptedElicitation with the extracted/validated data
### `get_elicitation_schema` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L369" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_elicitation_schema(response_type: type[T]) -> dict[str, Any]
```
Get the schema for an elicitation response.
**Args:**
- `response_type`: The type of the response
### `validate_elicitation_json_schema` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L395" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
validate_elicitation_json_schema(schema: dict[str, Any]) -> None
```
Validate that a JSON schema follows MCP elicitation requirements.
This ensures the schema is compatible with MCP elicitation requirements:
- Must be an object schema
- Must only contain primitive field types (string, number, integer, boolean)
- Must be flat (no nested objects or arrays of objects)
- Allows const fields (for Literal types) and enum fields (for Enum types)
- Only primitive types and their nullable variants are allowed
**Args:**
- `schema`: The JSON schema to validate
**Raises:**
- `TypeError`: If the schema doesn't meet MCP elicitation requirements
## Classes
### `ElicitationJsonSchema` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L36" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Custom JSON schema generator for MCP elicitation that always inlines enums.
MCP elicitation requires inline enum schemas without $ref/$defs references.
This generator ensures enums are always generated inline for compatibility.
Optionally adds enumNames for better UI display when available.
**Methods:**
#### `generate_inner` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L44" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
generate_inner(self, schema: core_schema.CoreSchema) -> JsonSchemaValue
```
Override to prevent ref generation for enums and handle list schemas.
#### `list_schema` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L57" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_schema(self, schema: core_schema.ListSchema) -> JsonSchemaValue
```
Generate schema for list types, detecting enum items for multi-select.
#### `enum_schema` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L94" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
enum_schema(self, schema: core_schema.EnumSchema) -> JsonSchemaValue
```
Generate inline enum schema.
Always generates enum pattern: `{"enum": [value, ...]}`
Titled enums are handled separately via dict-based syntax in ctx.elicit().
### `AcceptedElicitation` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L105" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Result when user accepts the elicitation.
### `ScalarElicitationType` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L113" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ElicitConfig` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/elicitation.py#L118" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Configuration for an elicitation request.
**Attributes:**
- `schema`: The JSON schema to send to the client
- `response_type`: The type to validate responses with (None for raw schemas)
- `is_raw`: True if schema was built directly (extract "value" from response)

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---
title: event_store
sidebarTitle: event_store
---
# `fastmcp.server.event_store`
EventStore implementation backed by AsyncKeyValue.
This module provides an EventStore implementation that enables SSE polling/resumability
for Streamable HTTP transports. Events are stored using the key_value package's
AsyncKeyValue protocol, allowing users to configure any compatible backend
(in-memory, Redis, etc.) following the same pattern as ResponseCachingMiddleware.
## Classes
### `EventEntry` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/event_store.py#L34" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Stored event entry.
### `StreamEventList` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/event_store.py#L42" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
List of event IDs for a stream.
### `EventStore` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/event_store.py#L48" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
EventStore implementation backed by AsyncKeyValue.
Enables SSE polling/resumability by storing events that can be replayed
when clients reconnect. Works with any AsyncKeyValue backend (memory, Redis, etc.)
following the same pattern as ResponseCachingMiddleware and OAuthProxy.
**Args:**
- `storage`: AsyncKeyValue backend. Defaults to MemoryStore.
- `max_events_per_stream`: Maximum events to retain per stream. Default 100.
- `ttl`: Event TTL in seconds. Default 3600 (1 hour). Set to None for no expiration.
**Methods:**
#### `store_event` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/event_store.py#L102" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
store_event(self, stream_id: StreamId, message: JSONRPCMessage | None) -> EventId
```
Store an event and return its ID.
**Args:**
- `stream_id`: ID of the stream the event belongs to
- `message`: The JSON-RPC message to store, or None for priming events
**Returns:**
- The generated event ID for the stored event
#### `replay_events_after` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/event_store.py#L143" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
replay_events_after(self, last_event_id: EventId, send_callback: EventCallback) -> StreamId | None
```
Replay events that occurred after the specified event ID.
**Args:**
- `last_event_id`: The ID of the last event the client received
- `send_callback`: A callback function to send events to the client
**Returns:**
- The stream ID of the replayed events, or None if the event ID was not found

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---
title: extensions
sidebarTitle: extensions
---
# `fastmcp.server.extensions`
FastMCP-native server extension API (SEP-2133).
An MCP extension is an opt-in, capability-negotiated bundle of protocol
behaviour identified by a reverse-DNS string (e.g. `io.modelcontextprotocol/tasks`).
Unlike the SDK's `mcp.server.extension.Extension`, a FastMCP `ServerExtension`
is bound to its `FastMCP` instance at registration, so its request handlers and
its `tools/call` interceptor can reach the component registry, `Context`, and
auth scope that the SDK's model withholds.
An extension contributes any subset of four things:
- **A negotiated capability.** `settings()` is spliced into
`ServerCapabilities.extensions[identifier]` (see `LowLevelServer.get_capabilities`).
- **New request methods.** `methods()` returns `MethodBinding`s, each wired onto
the low-level server via `add_request_handler` when the extension is registered.
- **A `tools/call` interceptor.** `intercept_tool_call()` is the last gate before
a tool body runs — it composes *after* the FastMCP middleware chain and *before*
component execution, so it can observe, short-circuit, or pass a call through.
- **A lifespan.** `lifespan()` is entered with the server's lifespan and exited on
shutdown — the hook the SDK's `Extension` lacks, needed to start backends/workers.
The base class follows the SDK's httpx-style shape: every contribution method has
a default, so a subclass overrides only what it needs.
## Functions
### `read_client_extension_settings` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L235" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
read_client_extension_settings(ctx: ServerRequestContext[Any, Any], identifier: str) -> dict[str, Any] | None
```
Read a client's per-request extension opt-in from the request `_meta`.
SEP-2133 extensions negotiate per request: the client repeats its extension
capabilities in each request's `_meta` under
`io.modelcontextprotocol/clientCapabilities` → `extensions` → `identifier`.
Returns the declared settings dict (possibly empty) when the extension was
opted in for this request, or `None` when it was not.
### `build_method_handler` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L249" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
build_method_handler(binding: MethodBinding) -> ExtensionRequestHandler
```
Wrap a `MethodBinding` into a low-level request handler.
The adapter enforces `protocol_versions` gating (rejecting other versions as
`METHOD_NOT_FOUND`, since `add_request_handler` registers unconditionally)
and binds the FastMCP request context so the handler can use `get_context()`,
auth, and other request-scoped dependencies.
### `wrap_tool_call_interceptor` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L278" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
wrap_tool_call_interceptor(extension: ServerExtension, call_next: Callable[[Any], Awaitable[Any]]) -> Callable[[Any], Awaitable[Any]]
```
Fold one extension's `intercept_tool_call` around a middleware `call_next`.
The returned wrapper is a FastMCP `CallNext`: it hands the extension the
validated `tools/call` params, the FastMCP `Context`, and a zero-arg
continuation that runs the rest of the chain and, finally, the tool body.
## Classes
### `MethodBinding` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L77" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
A new request method an extension serves, e.g. `tasks/get`.
`params_type` validates incoming params before `handler` runs; it should
subclass `RequestParams` so `_meta` parses uniformly. `protocol_versions`,
when set, restricts the method to those wire versions — a request at any
other version is rejected as `METHOD_NOT_FOUND`, mirroring the spec's
`(method, version)` boundary. `None` (the default) admits every version.
Extension methods are additive: `method` must not name a spec-defined
request method (`tools/call`, `completion/complete`, ...). Binding one would
silently shadow the server's own handler. Both constraints are enforced at
construction.
### `ServerExtension` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L111" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Base class for an opt-in FastMCP server extension (SEP-2133).
Subclass, set `identifier`, and override the contribution methods that
apply. Every method has a default, so a minimal extension overrides only
`identifier` and one contribution. `identifier` is validated at
subclass-definition time when set as a class attribute, and again at
registration (which covers per-instance identifiers assigned in `__init__`).
Register an instance with `FastMCP.add_extension(...)`, which binds the
extension to the server so `self.server`, `intercept_tool_call`, and method
handlers can reach FastMCP-level constructs.
**Methods:**
#### `server` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L149" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
server(self) -> FastMCP
```
The FastMCP server this extension is registered on.
Handlers, interceptors, and lifespan code reach the component registry,
`Context`, and auth scope through here. Raises if the extension has not
been registered with `FastMCP.add_extension()`.
#### `settings` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L165" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
settings(self) -> dict[str, Any]
```
Per-extension settings advertised at `capabilities.extensions[identifier]`.
An empty dict (the default) advertises the extension with no settings.
#### `methods` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L172" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
methods(self) -> Sequence[MethodBinding]
```
New request methods this extension serves (additive).
#### `lifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L176" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
lifespan(self) -> AbstractAsyncContextManager[None]
```
A context manager entered with the server's lifespan, exited on shutdown.
Default: a no-op. Override to start and stop resources an extension owns
(a task-queue backend and worker, say). Entered once per runtime tree, at
the root — a mounted child defers to the root, as the shared Docket does.
#### `intercept_tool_call` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L185" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
intercept_tool_call(self, params: CallToolRequestParams, context: Context, call_next: ToolCallContinuation) -> ToolCallOutcome
```
Wrap `tools/call`. Default: pass through unchanged.
Runs after the FastMCP middleware chain and before the tool body, so it
is the last gate before execution. Override to observe the call, to
short-circuit (return a result without awaiting `call_next`), or to pass
it through (`return await call_next()`). `params` is the validated
`tools/call` params; `context` is the FastMCP `Context`, from which the
tool being called (`context.fastmcp.get_tool(params.name)`), auth scope,
and the server are reachable. Multiple extensions nest with the
first-registered outermost.
#### `client_settings` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/extensions.py#L204" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
client_settings(self, ctx: ServerRequestContext[Any, Any]) -> dict[str, Any] | None
```
This extension's per-request opt-in settings declared by the client.
Reads the request's `_meta` client-capabilities block. Returns the
declared settings dict (possibly empty) when the client opted this
extension in for the request, or `None` when it did not. Convenience for
`read_client_extension_settings(ctx, self.identifier)`.

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---
title: http
sidebarTitle: http
---
# `fastmcp.server.http`
## Functions
### `set_http_request` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L355" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_http_request(request: Request) -> Generator[Request, None, None]
```
### `create_base_app` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L388" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
create_base_app(routes: list[BaseRoute], middleware: list[Middleware], debug: bool = False, lifespan: Callable | None = None) -> StarletteWithLifespan
```
Create a base Starlette app with common middleware and routes.
**Args:**
- `routes`: List of routes to include in the app
- `middleware`: List of middleware to include in the app
- `debug`: Whether to enable debug mode
- `lifespan`: Optional lifespan manager for the app
**Returns:**
- A Starlette application
### `create_sse_app` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L416" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
create_sse_app(server: FastMCP[LifespanResultT], message_path: str, sse_path: str, auth: AuthProvider | None = None, debug: bool = False, routes: list[BaseRoute] | None = None, middleware: list[Middleware] | None = None) -> StarletteWithLifespan
```
Return an instance of the SSE server app.
**Args:**
- `server`: The FastMCP server instance
- `message_path`: Path for SSE messages
- `sse_path`: Path for SSE connections
- `auth`: Optional authentication provider (AuthProvider)
- `debug`: Whether to enable debug mode
- `routes`: Optional list of custom routes
- `middleware`: Optional list of middleware
Returns:
A Starlette application with RequestContextMiddleware
### `create_streamable_http_app` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L545" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
create_streamable_http_app(server: FastMCP[LifespanResultT], streamable_http_path: str, event_store: EventStore | None = None, retry_interval: int | None = None, auth: AuthProvider | None = None, json_response: bool = False, stateless_http: bool = False, debug: bool = False, routes: list[BaseRoute] | None = None, middleware: list[Middleware] | None = None, host_origin_protection: HostOriginProtection = False, allowed_hosts: Sequence[str] | None = None, allowed_origins: Sequence[str] | None = None, session_idle_timeout: float | None = None) -> StarletteWithLifespan
```
Return an instance of the StreamableHTTP server app.
**Args:**
- `server`: The FastMCP server instance
- `streamable_http_path`: Path for StreamableHTTP connections
- `event_store`: Optional event store for SSE polling/resumability
- `retry_interval`: Optional retry interval in milliseconds for SSE polling.
Controls how quickly clients should reconnect after server-initiated
disconnections. Requires event_store to be set. Defaults to SDK default.
- `auth`: Optional authentication provider (AuthProvider)
- `json_response`: Whether to use JSON response format
- `stateless_http`: Whether to use stateless mode (new transport per request)
- `debug`: Whether to enable debug mode
- `routes`: Optional list of custom routes
- `middleware`: Optional list of middleware
- `host_origin_protection`: Whether to validate Host and Origin headers
before requests reach the MCP endpoint. Defaults to False for
compatibility. "auto" protects localhost-bound servers and explicit
host/origin allowlists.
- `allowed_hosts`: Additional hostnames that may appear in the Host header.
- `allowed_origins`: Additional browser origins trusted by the request guard.
Configure CORS separately when browser JavaScript must read
cross-origin responses.
- `session_idle_timeout`: Maximum time in seconds a session may remain idle
before it is terminated. The deadline is pushed forward on every
request. When None, sessions never expire from inactivity. Not
supported in stateless mode.
**Returns:**
- A Starlette application with StreamableHTTP support
## Classes
### `FastMCPStreamableHTTPSessionManager` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L43" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Session manager that scopes resumability storage per transport session.
**Methods:**
#### `event_store` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L68" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
event_store(self) -> EventStore | None
```
#### `event_store` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L76" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
event_store(self, event_store: EventStore | None) -> None
```
### `StreamableHTTPASGIApp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L80" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
ASGI application wrapper for Streamable HTTP server transport.
### `HostOriginGuardMiddleware` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L227" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Validate Host and Origin headers before requests reach MCP sessions.
### `StarletteWithLifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L348" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
**Methods:**
#### `lifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L350" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
lifespan(self) -> Lifespan[Starlette]
```
### `RequestContextMiddleware` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L363" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Middleware that stores each request in a ContextVar and sets transport type.

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---
title: lifespan
sidebarTitle: lifespan
---
# `fastmcp.server.lifespan`
Composable lifespans for FastMCP servers.
This module provides a `@lifespan` decorator for creating composable server lifespans
that can be combined using the `|` operator.
Example:
```python
from fastmcp import FastMCP
from fastmcp.server.lifespan import lifespan
@lifespan
async def db_lifespan(server):
conn = await connect_db()
yield {"db": conn}
await conn.close()
@lifespan
async def cache_lifespan(server):
cache = await connect_cache()
yield {"cache": cache}
await cache.close()
mcp = FastMCP("server", lifespan=db_lifespan | cache_lifespan)
```
To compose with existing `@asynccontextmanager` lifespans, wrap them explicitly:
```python
from contextlib import asynccontextmanager
from fastmcp.server.lifespan import lifespan, ContextManagerLifespan
@asynccontextmanager
async def legacy_lifespan(server):
yield {"legacy": True}
@lifespan
async def new_lifespan(server):
yield {"new": True}
# Wrap the legacy lifespan explicitly
combined = ContextManagerLifespan(legacy_lifespan) | new_lifespan
```
## Functions
### `lifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/lifespan.py#L172" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
lifespan(fn: LifespanFn) -> Lifespan
```
Decorator to create a composable lifespan.
Use this decorator on an async generator function to make it composable
with other lifespans using the `|` operator.
**Args:**
- `fn`: An async generator function that takes a FastMCP server and yields
a dict for the lifespan context.
**Returns:**
- A composable Lifespan wrapper.
## Classes
### `Lifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/lifespan.py#L61" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Composable lifespan wrapper.
Wraps an async generator function and enables composition via the `|` operator.
The wrapped function should yield a dict that becomes part of the lifespan context.
### `ContextManagerLifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/lifespan.py#L110" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Lifespan wrapper for already-wrapped context manager functions.
Use this for functions already decorated with @asynccontextmanager.
### `ComposedLifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/lifespan.py#L137" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Two lifespans composed together.
Enters the left lifespan first, then the right. Exits in reverse order.
Results are shallow-merged into a single dict.

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---
title: low_level
sidebarTitle: low_level
---
# `fastmcp.server.low_level`
## Functions
### `client_supports_extension` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/low_level.py#L111" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
client_supports_extension(session: ServerSession, extension_id: str) -> bool
```
Check whether the connected client supports a given MCP extension.
Inspects the ``extensions`` capability on ``ClientCapabilities`` sent by the
client during initialization. In v2 the client's initialize params are
reachable via ``session.client_params``.
SDK v2 declares ``extensions`` as a real field on ``ClientCapabilities``, so
a client sending ``ClientCapabilities(extensions={...})`` populates the field
directly. We read that field first and fall back to ``model_extra`` only for
legacy-serialized clients that carried ``extensions`` as an extra key.
## Classes
### `FastMCPServerMiddleware` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/low_level.py#L140" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Root dispatch for the FastMCP middleware chain, in the SDK's middleware layer.
v2 no longer lets FastMCP subclass ``ServerSession`` (the runner constructs
it per request), so the old ``MiddlewareServerSession._received_request``
override is replaced by a ``ServerMiddleware`` — an ordinary entry in the
SDK's own middleware list. Sitting at the root of dispatch, this
is the single entry point through which *every* inbound message flows —
requests, notifications, cancellations, ``initialize``, and even malformed or
unroutable messages the SDK can still hand us. It binds the FastMCP
request-context ContextVar and re-applies the app-scoped ``SharedContext`` for
the whole chain, then runs the FastMCP ``Middleware`` chain so
``on_message`` / ``on_request`` / ``on_notification`` observe the message.
Dispatch shapes:
- Negotiation runs the *whole* FastMCP chain here: ``initialize`` dispatches
through ``on_initialize`` and ``server/discover`` through ``on_discover``.
Neither has an interior FastMCP handler adapter, and the SDK serializes both
results before returning through its middleware seam, so this root adapter
restores core results to typed models before FastMCP middleware observes them.
- The component methods (``tools/call``, ``tools/list``, ``resources/read``,
...) still run their FastMCP chain *interior*, in the handler adapter, where
``on_call_tool`` receives the typed component result and a tool exception
propagates through ``on_message``/``on_request`` exactly where the built-in
error/logging/timing middleware expect it. The root dispatch does not re-run the
chain for these — it only steps in when such a request fails *before* the
interior runs (malformed params, routing), so ``on_message`` still observes
the failure.
- Every other message — all notifications (including ``notifications/cancelled``
and ``notifications/initialized``), ``ping``, ``logging/setLevel``, and any
unroutable/non-component request — has no interior FastMCP dispatch, so the
root dispatch runs the ``"outer"`` pass (``on_message`` plus
``on_request``/``on_notification``) here, wrapping the real SDK dispatch.
This closes the long-standing gap where these messages were invisible to
FastMCP middleware.
### `LowLevelServer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/low_level.py#L455" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
**Methods:**
#### `fastmcp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/low_level.py#L507" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
fastmcp(self) -> FastMCP
```
Get the FastMCP instance.
#### `create_initialization_options` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/low_level.py#L514" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
create_initialization_options(self, notification_options: NotificationOptions | None = None, experimental_capabilities: dict[str, dict[str, Any]] | None = None, extensions: dict[str, dict[str, Any]] | None = None) -> InitializationOptions
```
#### `get_capabilities` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/low_level.py#L529" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_capabilities(self, notification_options: NotificationOptions | None = None, experimental_capabilities: dict[str, dict[str, Any]] | None = None, extensions: dict[str, dict[str, Any]] | None = None) -> mcp_types.ServerCapabilities
```
Override to advertise registered extensions and the MCP Apps UI extension.
``ServerCapabilities.extensions`` is a real declared field in v2, so we
update it directly. The
`FastMCP(experimental_capabilities=...)` merge also lives here rather
than in `create_initialization_options`: the modern `server/discover`
handler calls this directly, without going through
`create_initialization_options` at all, so merging there only reached
the handshake-era `initialize` response and silently dropped
constructor-configured experimental capabilities from `discover`.

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---
title: mixins
sidebarTitle: mixins
---
# `fastmcp.server.mixins`
Server mixins for FastMCP.

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---
title: providers
sidebarTitle: providers
---
# `fastmcp.server.providers`
Providers for dynamic MCP components.
This module provides the `Provider` abstraction for providing tools,
resources, and prompts dynamically at runtime.
Example:
```python
from fastmcp import FastMCP
from fastmcp.server.providers import Provider
from fastmcp.tools import Tool
class DatabaseProvider(Provider):
def __init__(self, db_url: str):
self.db = Database(db_url)
async def _list_tools(self) -> list[Tool]:
rows = await self.db.fetch("SELECT * FROM tools")
return [self._make_tool(row) for row in rows]
async def _get_tool(self, name: str) -> Tool | None:
row = await self.db.fetchone("SELECT * FROM tools WHERE name = ?", name)
return self._make_tool(row) if row else None
mcp = FastMCP("Server", providers=[DatabaseProvider(db_url)])
```

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---
title: server
sidebarTitle: server
---
# `fastmcp.server.server`
FastMCP - A more ergonomic interface for MCP servers.
## Functions
### `default_lifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L237" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
default_lifespan(server: FastMCP[LifespanResultT]) -> AsyncIterator[Any]
```
Default lifespan context manager that does nothing.
**Args:**
- `server`: The server instance this lifespan is managing
**Returns:**
- An empty dictionary as the lifespan result.
### `create_proxy` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2501" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
create_proxy(target: Client[ClientTransportT] | ClientTransport | FastMCP[Any] | SDKServer | AnyUrl | Path | MCPConfig | dict[str, Any] | str, **settings: Any) -> FastMCPProxy
```
Create a FastMCP proxy server for the given target.
This is the recommended way to create a proxy server. For lower-level control,
use `FastMCPProxy` or `ProxyProvider` directly from `fastmcp.server.providers.proxy`.
**Args:**
- `target`: The backend to proxy to. Can be\:
- A Client instance (connected or disconnected)
- A ClientTransport
- A FastMCP server instance
- A URL string or AnyUrl
- A Path to a server script
- An MCPConfig or dict
- `mode`: Protocol-era negotiation for auto-created proxy clients (a
non-Client target). By default (``None``) the backend MIRRORS the
front connection's negotiated era per request, so the whole chain
speaks one era end-to-end\: a modern front reaches a modern backend
(a guard tool's `InputRequiredResult` (SEP-2322) round-trips) and a
handshake front reaches a handshake backend (server-initiated
sampling / elicitation / roots push-forwarding works). Pass an
explicit mode (e.g. ``"auto"`` or a version string) to pin the
backend era regardless of the front; this overrides mirroring and is
appropriate when the backend only speaks one era. Ignored when
`target` is already a `Client` (which carries its own mode).
- `**settings`: Additional settings passed to FastMCPProxy (name, etc.)
**Returns:**
- A FastMCPProxy server that proxies to the target.
## Classes
### `StateValue` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L272" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Wrapper for stored context state values.
### `FastMCP` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L278" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
**Methods:**
#### `name` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L507" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
name(self) -> str
```
#### `instructions` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L511" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
instructions(self) -> str | None
```
#### `instructions` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L515" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
instructions(self, value: str | None) -> None
```
#### `version` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L519" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
version(self) -> str | None
```
#### `website_url` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L523" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
website_url(self) -> str | None
```
#### `icons` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L527" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
icons(self) -> list[mcp_types.Icon]
```
#### `local_provider` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L534" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
local_provider(self) -> LocalProvider
```
The server's local provider, which stores directly-registered components.
Use this to remove components:
mcp.local_provider.remove_tool("my_tool")
mcp.local_provider.remove_resource("data://info")
mcp.local_provider.remove_prompt("my_prompt")
#### `add_middleware` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L598" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_middleware(self, middleware: Middleware) -> None
```
#### `add_extension` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L601" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_extension(self, extension: ServerExtension) -> None
```
Register a server extension (SEP-2133).
An extension contributes a negotiated capability, additive request
methods, a `tools/call` interceptor, and an optional lifespan — each
with access to FastMCP-level constructs (the component registry,
`Context`, auth scope). Its capability is advertised only while it is
registered.
The extension is bound to this server (so its handlers and interceptor
can reach it), its method bindings are wired onto the low-level server,
and it is recorded for capability advertisement, interception, and
lifespan entry. Registering two extensions with the same identifier is
an error, as is registering after the server's lifespan has started —
the extension's lifespan could no longer run, leaving it silently
half-active.
Extensions are served by the server they are registered on. A mounted
child's extensions do not propagate to the root: the root serves the
wire, so only root-registered extensions advertise capabilities and
answer methods (matching the lifespan, which also defers to the root).
Register extensions on the server you run.
#### `add_provider` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L673" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_provider(self, provider: Provider) -> None
```
Add a provider for dynamic tools, resources, and prompts.
Providers are queried in registration order. The first provider to return
a non-None result wins. Static components (registered via decorators)
always take precedence over providers.
**Args:**
- `provider`: A Provider instance that will provide components dynamically.
- `namespace`: Optional namespace prefix. When set\:
- Tools become "namespace_toolname"
- Resources become "protocol\://namespace/path"
- Prompts become "namespace_promptname"
#### `get_tasks` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L785" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_tasks(self) -> Sequence[FastMCPComponent]
```
Get task-eligible components with all transforms applied.
Overrides AggregateProvider.get_tasks() to apply server-level transforms
after aggregation. AggregateProvider handles provider-level namespacing.
#### `add_transform` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L814" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_transform(self, transform: Transform) -> None
```
Add a server-level transform.
Server-level transforms are applied after all providers are aggregated.
They transform tools, resources, and prompts from ALL providers.
**Args:**
- `transform`: The transform to add.
#### `list_tools` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L834" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_tools(self) -> Sequence[Tool]
```
List all enabled tools from providers.
Overrides Provider.list_tools() to add enabled filtering, auth filtering,
and middleware execution. Returns all versions (no deduplication).
Protocol handlers deduplicate for MCP wire format.
#### `get_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L917" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_tool(self, name: str, version: VersionSpec | None = None) -> Tool | None
```
Get a tool by name, filtering disabled tools.
Overrides Provider.get_tool() to filter disabled tools after all
transforms (including session-level) have been applied. This ensures
session transforms can override provider-level disables.
When the highest version is disabled and no explicit version was
requested, falls back to the next-highest enabled version.
**Args:**
- `name`: The tool name.
- `version`: Version filter (None returns highest version).
**Returns:**
- The tool if found and enabled, None otherwise.
#### `list_resources` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L971" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_resources(self) -> Sequence[Resource]
```
List all enabled resources from providers.
Overrides Provider.list_resources() to add visibility filtering, auth filtering,
and middleware execution. Returns all versions (no deduplication).
Protocol handlers deduplicate for MCP wire format.
#### `get_resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1056" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_resource(self, uri: str, version: VersionSpec | None = None) -> Resource | None
```
Get a resource by URI, filtering disabled resources.
Overrides Provider.get_resource() to add visibility filtering after all
transforms (including session-level) have been applied.
When the highest version is disabled and no explicit version was
requested, falls back to the next-highest enabled version.
**Args:**
- `uri`: The resource URI.
- `version`: Version filter (None returns highest version).
**Returns:**
- The resource if found and enabled, None otherwise.
#### `list_resource_templates` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1106" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_resource_templates(self) -> Sequence[ResourceTemplate]
```
List all enabled resource templates from providers.
Overrides Provider.list_resource_templates() to add visibility filtering,
auth filtering, and middleware execution. Returns all versions (no deduplication).
Protocol handlers deduplicate for MCP wire format.
#### `get_resource_template` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1188" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_resource_template(self, uri: str, version: VersionSpec | None = None) -> ResourceTemplate | None
```
Get a resource template by URI, filtering disabled templates.
Overrides Provider.get_resource_template() to add visibility filtering after
all transforms (including session-level) have been applied.
When the highest version is disabled and no explicit version was
requested, falls back to the next-highest enabled version.
**Args:**
- `uri`: The template URI.
- `version`: Version filter (None returns highest version).
**Returns:**
- The template if found and enabled, None otherwise.
#### `list_prompts` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1242" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_prompts(self) -> Sequence[Prompt]
```
List all enabled prompts from providers.
Overrides Provider.list_prompts() to add visibility filtering, auth filtering,
and middleware execution. Returns all versions (no deduplication).
Protocol handlers deduplicate for MCP wire format.
#### `get_prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1314" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_prompt(self, name: str, version: VersionSpec | None = None) -> Prompt | None
```
Get a prompt by name, filtering disabled prompts.
Overrides Provider.get_prompt() to add visibility filtering after all
transforms (including session-level) have been applied.
When the highest version is disabled and no explicit version was
requested, falls back to the next-highest enabled version.
**Args:**
- `name`: The prompt name.
- `version`: Version filter (None returns highest version).
**Returns:**
- The prompt if found and enabled, None otherwise.
#### `call_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1364" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
call_tool(self, name: str, arguments: dict[str, Any] | None = None) -> ToolResult
```
Call a tool by name.
This is the public API for executing tools. By default, middleware is applied.
**Args:**
- `name`: The tool name
- `arguments`: Tool arguments (optional)
- `version`: Specific version to call. If None, calls highest version.
- `run_middleware`: If True (default), apply the middleware chain.
Set to False when called from middleware to avoid re-applying.
**Returns:**
- ToolResult.
A guard tool that requests client input (SEP-2322 multi-round-trip)
returns an ``InputRequiredToolResult`` (a ``ToolResult`` subclass); it
flows back through the middleware chain as an ordinary result and the
wire handler unwraps it into an ``InputRequiredResult`` on the response.
**Raises:**
- `NotFoundError`: If tool not found or disabled
- `ToolError`: If tool execution fails
- `ValidationError`: If arguments fail validation
#### `read_resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1557" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
read_resource(self, uri: str) -> ResourceResult
```
Read a resource by URI.
This is the public API for reading resources. By default, middleware is applied.
Checks concrete resources first, then templates.
**Args:**
- `uri`: The resource URI
- `version`: Specific version to read. If None, reads highest version.
- `run_middleware`: If True (default), apply the middleware chain.
Set to False when called from middleware to avoid re-applying.
**Returns:**
- ResourceResult.
**Raises:**
- `NotFoundError`: If resource not found or disabled
- `ResourceError`: If resource read fails
#### `render_prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1715" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
render_prompt(self, name: str, arguments: dict[str, Any] | None = None) -> PromptResult
```
Render a prompt by name.
This is the public API for rendering prompts. By default, middleware is applied.
Use get_prompt() to retrieve the prompt definition without rendering.
**Args:**
- `name`: The prompt name
- `arguments`: Prompt arguments (optional)
- `version`: Specific version to render. If None, renders highest version.
- `run_middleware`: If True (default), apply the middleware chain.
Set to False when called from middleware to avoid re-applying.
**Returns:**
- PromptResult.
**Raises:**
- `NotFoundError`: If prompt not found or disabled
- `PromptError`: If prompt rendering fails
#### `add_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1795" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_tool(self, tool: Tool | Callable[..., Any]) -> Tool
```
Add a tool to the server.
The tool function can optionally request a Context object by adding a parameter
with the Context type annotation. See the @tool decorator for examples.
**Args:**
- `tool`: The Tool instance or @tool-decorated function to register
**Returns:**
- The tool instance that was added to the server.
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1810" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
tool(self, name_or_fn: F) -> F
```
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1831" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
tool(self, name_or_fn: str | None = None) -> Callable[[F], F]
```
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1851" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
tool(self, name_or_fn: str | AnyFunction | None = None) -> Callable[[AnyFunction], FunctionTool] | FunctionTool | partial[Callable[[AnyFunction], FunctionTool] | FunctionTool]
```
Decorator to register a tool.
Tools can optionally request a Context object by adding a parameter with the
Context type annotation. The context provides access to MCP capabilities like
logging, progress reporting, and resource access.
This decorator supports multiple calling patterns:
- @server.tool (without parentheses)
- @server.tool (with empty parentheses)
- @server.tool("custom_name") (with name as first argument)
- @server.tool(name="custom_name") (with name as keyword argument)
- server.tool(function, name="custom_name") (direct function call)
**Args:**
- `name_or_fn`: Either a function (when used as @tool), a string name, or None
- `name`: Optional name for the tool (keyword-only, alternative to name_or_fn)
- `description`: Optional description of what the tool does
- `tags`: Optional set of tags for categorizing the tool
- `output_schema`: Optional JSON schema for the tool's output
- `annotations`: Optional annotations about the tool's behavior
- `meta`: Optional meta information about the tool
**Examples:**
Register a tool with a custom name:
```python
@server.tool
def my_tool(x: int) -> str:
return str(x)
# Register a tool with a custom name
@server.tool
def my_tool(x: int) -> str:
return str(x)
@server.tool("custom_name")
def my_tool(x: int) -> str:
return str(x)
@server.tool(name="custom_name")
def my_tool(x: int) -> str:
return str(x)
# Direct function call
server.tool(my_function, name="custom_name")
```
#### `add_resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1948" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_resource(self, resource: Resource | Callable[..., Any]) -> Resource | ResourceTemplate
```
Add a resource to the server.
**Args:**
- `resource`: A Resource instance or @resource-decorated function to add
**Returns:**
- The resource instance that was added to the server.
#### `add_template` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1961" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_template(self, template: ResourceTemplate) -> ResourceTemplate
```
Add a resource template to the server.
**Args:**
- `template`: A ResourceTemplate instance to add
**Returns:**
- The template instance that was added to the server.
#### `resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L1972" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
resource(self, uri: str) -> Callable[[F], F]
```
Decorator to register a function as a resource.
The function will be called when the resource is read to generate its content.
The function can return:
- str for text content
- bytes for binary content
- other types will be converted to JSON
Resources can optionally request a Context object by adding a parameter with the
Context type annotation. The context provides access to MCP capabilities like
logging, progress reporting, and session information.
If the URI contains parameters (e.g. "resource://{param}") or the function
has parameters, it will be registered as a template resource.
**Args:**
- `uri`: URI for the resource (e.g. "resource\://my-resource" or "resource\://{param}")
- `name`: Optional name for the resource
- `description`: Optional description of the resource
- `mime_type`: Optional MIME type for the resource
- `tags`: Optional set of tags for categorizing the resource
- `annotations`: Optional annotations about the resource's behavior
- `meta`: Optional meta information about the resource
**Examples:**
Register a resource with a custom name:
```python
@server.resource("resource://my-resource")
def get_data() -> str:
return "Hello, world!"
@server.resource("resource://my-resource")
async get_data() -> str:
data = await fetch_data()
return f"Hello, world! {data}"
@server.resource("resource://{city}/weather")
def get_weather(city: str) -> str:
return f"Weather for {city}"
@server.resource("resource://{city}/weather")
async def get_weather_with_context(city: str, ctx: Context) -> str:
await ctx.info(f"Fetching weather for {city}")
return f"Weather for {city}"
@server.resource("resource://{city}/weather")
async def get_weather(city: str) -> str:
data = await fetch_weather(city)
return f"Weather for {city}: {data}"
```
#### `add_prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2091" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_prompt(self, prompt: Prompt | Callable[..., Any]) -> Prompt
```
Add a prompt to the server.
**Args:**
- `prompt`: A Prompt instance or @prompt-decorated function to add
**Returns:**
- The prompt instance that was added to the server.
#### `prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2103" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
prompt(self, name_or_fn: F) -> F
```
#### `prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2118" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
prompt(self, name_or_fn: str | None = None) -> Callable[[F], F]
```
#### `prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2132" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
prompt(self, name_or_fn: str | AnyFunction | None = None) -> Callable[[AnyFunction], FunctionPrompt] | FunctionPrompt | partial[Callable[[AnyFunction], FunctionPrompt] | FunctionPrompt]
```
Decorator to register a prompt.
Prompts can optionally request a Context object by adding a parameter with the
Context type annotation. The context provides access to MCP capabilities like
logging, progress reporting, and session information.
This decorator supports multiple calling patterns:
- @server.prompt (without parentheses)
- @server.prompt() (with empty parentheses)
- @server.prompt("custom_name") (with name as first argument)
- @server.prompt(name="custom_name") (with name as keyword argument)
- server.prompt(function, name="custom_name") (direct function call)
Args:
name_or_fn: Either a function (when used as @prompt), a string name, or None
name: Optional name for the prompt (keyword-only, alternative to name_or_fn)
description: Optional description of what the prompt does
tags: Optional set of tags for categorizing the prompt
meta: Optional meta information about the prompt
Examples:
```python
@server.prompt
def analyze_table(table_name: str) -> list[Message]:
schema = read_table_schema(table_name)
return [
{
"role": "user",
"content": f"Analyze this schema:
{schema}"
}
]
@server.prompt()
async def analyze_with_context(table_name: str, ctx: Context) -> list[Message]:
await ctx.info(f"Analyzing table {table_name}")
schema = read_table_schema(table_name)
return [
{
"role": "user",
"content": f"Analyze this schema:
{schema}"
}
]
@server.prompt("custom_name")
async def analyze_file(path: str) -> list[Message]:
content = await read_file(path)
return [
{
"role": "user",
"content": {
"type": "resource",
"resource": {
"uri": f"file://{path}",
"text": content
}
}
}
]
@server.prompt(name="custom_name")
def another_prompt(data: str) -> list[Message]:
return [{"role": "user", "content": data}]
# Direct function call
server.prompt(my_function, name="custom_name")
```
#### `add_completion_handler` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2230" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_completion_handler(self, handler: CompletionHandler) -> None
```
Register the server's argument-completion handler.
A server has a single completion handler that answers every
`completion/complete` request, switching on the reference (a prompt or
resource template) and the argument being completed. Registering it also
registers the low-level `completion/complete` handler, which is what
makes the SDK declare the completions capability — so the capability is
advertised exactly when the server can answer. Calling this again
replaces the handler.
**Args:**
- `handler`: A callable taking the reference, the
`CompletionArgument`, and the optional `CompletionContext`, and
returning candidate values (a `Completion`, a list of strings,
or None). May be sync or async.
#### `completion` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2251" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
completion(self, handler: CompletionHandler) -> CompletionHandler
```
#### `completion` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2254" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
completion(self) -> Callable[[CompletionHandler], CompletionHandler]
```
#### `completion` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2258" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
completion(self, handler: CompletionHandler | None = None) -> CompletionHandler | Callable[[CompletionHandler], CompletionHandler]
```
Decorator to register the server's argument-completion handler.
The handler answers `completion/complete` requests for prompt arguments
and resource-template parameters. It receives the reference being
completed, the argument (its name and the partial value typed so far),
and the context of arguments already supplied, and returns candidate
values. Return a list of strings, a `Completion` (to include pagination
hints), or None when the reference/argument is not one it handles — an
unhandled reference yields an empty completion, not an error.
Registering a handler declares the completions capability; a server with
none does not advertise it. This works identically on the handshake and
modern protocol eras.
Supports both `@mcp.completion` and `@mcp.completion()`.
Example:
```python
from fastmcp import FastMCP
from mcp_types import Completion, PromptReference
mcp = FastMCP("Completion Server")
@mcp.prompt
def poem(theme: str) -> str:
return f"Write a poem about {theme}"
@mcp.completion
def complete(ref, argument, context):
if isinstance(ref, PromptReference) and ref.name == "poem":
if argument.name == "theme":
options = ["nature", "love", "adventure"]
return [o for o in options if o.startswith(argument.value)]
return None
```
#### `mount` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2308" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
mount(self, server: FastMCP[LifespanResultT], namespace: str | None = None, tool_names: dict[str, str] | None = None) -> None
```
Mount another FastMCP server on this server with an optional namespace.
Mounting establishes a dynamic connection between servers. When a client
interacts with a mounted server's objects through the parent server, requests
are forwarded to the mounted server in real-time. This means changes to the
mounted server are immediately reflected when accessed through the parent.
When a server is mounted with a namespace:
- Tools from the mounted server are accessible with namespaced names.
Example: If server has a tool named "get_weather", it will be available as "namespace_get_weather".
- Resources are accessible with namespaced URIs.
Example: If server has a resource with URI "weather://forecast", it will be available as
"weather://namespace/forecast".
- Templates are accessible with namespaced URI templates.
Example: If server has a template with URI "weather://location/{id}", it will be available
as "weather://namespace/location/{id}".
- Prompts are accessible with namespaced names.
Example: If server has a prompt named "weather_prompt", it will be available as
"namespace_weather_prompt".
When a server is mounted without a namespace (namespace=None), its tools, resources, templates,
and prompts are accessible with their original names. Multiple servers can be mounted
without namespaces, and they will be tried in order until a match is found.
The mounted server's lifespan is executed when the parent server starts, and its
middleware chain is invoked for all operations (tool calls, resource reads, prompts).
**Args:**
- `server`: The FastMCP server to mount.
- `namespace`: Optional namespace to use for the mounted server's objects. If None,
the server's objects are accessible with their original names.
- `tool_names`: Optional mapping of original tool names to custom names. Use this
to override namespaced names. Keys are the original tool names from the
mounted server.
#### `from_openapi` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2379" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
from_openapi(cls, openapi_spec: dict[str, Any], client: httpx2.AsyncClient | None = None, name: str = 'OpenAPI Server', route_maps: list[RouteMap] | None = None, route_map_fn: OpenAPIRouteMapFn | None = None, mcp_component_fn: OpenAPIComponentFn | None = None, mcp_names: dict[str, str] | None = None, tags: set[str] | None = None, validate_output: bool = True, **settings: Any) -> Self
```
Create a FastMCP server from an OpenAPI specification.
**Args:**
- `openapi_spec`: OpenAPI schema as a dictionary
- `client`: Optional httpx2 AsyncClient for making HTTP requests.
If not provided, a default client is created using the first
server URL from the OpenAPI spec with a 30-second timeout.
Legacy httpx clients are temporarily accepted with a deprecation
warning.
- `name`: Name for the MCP server
- `route_maps`: Optional list of RouteMap objects defining route mappings
- `route_map_fn`: Optional callable for advanced route type mapping
- `mcp_component_fn`: Optional callable for component customization
- `mcp_names`: Optional dictionary mapping operationId to component names
- `tags`: Optional set of tags to add to all components
- `validate_output`: If True (default), tools use the output schema
extracted from the OpenAPI spec for response validation. If
False, a permissive schema is used instead, allowing any
response structure while still returning structured JSON.
- `**settings`: Additional settings passed to FastMCP
**Returns:**
- A FastMCP server with an OpenAPIProvider attached.
#### `from_fastapi` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2432" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
from_fastapi(cls, app: Any, name: str | None = None, route_maps: list[RouteMap] | None = None, route_map_fn: OpenAPIRouteMapFn | None = None, mcp_component_fn: OpenAPIComponentFn | None = None, mcp_names: dict[str, str] | None = None, httpx_client_kwargs: dict[str, Any] | None = None, tags: set[str] | None = None, **settings: Any) -> Self
```
Create a FastMCP server from a FastAPI application.
**Args:**
- `app`: FastAPI application instance
- `name`: Name for the MCP server (defaults to app.title)
- `route_maps`: Optional list of RouteMap objects defining route mappings
- `route_map_fn`: Optional callable for advanced route type mapping
- `mcp_component_fn`: Optional callable for component customization
- `mcp_names`: Optional dictionary mapping operationId to component names
- `httpx_client_kwargs`: Optional kwargs passed to httpx2.AsyncClient.
Use this to configure timeout and other client settings.
- `tags`: Optional set of tags to add to all components
- `**settings`: Additional settings passed to FastMCP
**Returns:**
- A FastMCP server with an OpenAPIProvider attached.
#### `generate_name` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/server.py#L2487" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
generate_name(cls, name: str | None = None) -> str
```

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@ -0,0 +1,31 @@
---
title: session_scoped_event_store
sidebarTitle: session_scoped_event_store
---
# `fastmcp.server.session_scoped_event_store`
Lightweight session scoping for Streamable HTTP event stores.
## Classes
### `SessionScopedEventStore` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/session_scoped_event_store.py#L19" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
EventStore adapter that isolates stream IDs to one transport session.
**Methods:**
#### `store_event` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/session_scoped_event_store.py#L34" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
store_event(self, stream_id: StreamId, message: JSONRPCMessage | None) -> EventId
```
#### `replay_events_after` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/session_scoped_event_store.py#L41" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
replay_events_after(self, last_event_id: EventId, send_callback: EventCallback) -> StreamId | None
```

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@ -0,0 +1,319 @@
---
title: sessions
sidebarTitle: sessions
---
# `fastmcp.server.sessions`
Stateless session state: server-side per-user and per-session storage.
Modern (2026-07-28) MCP connections are stateless by construction — every
request builds a fresh connection whose in-memory state is discarded when the
request returns. This module gives tools two explicit ways to keep state across
calls, both backed by the server's existing state store and both isolated by the
authenticated principal rather than by any client-declared identifier.
- `Session`: async `get`/`set`/`delete`/`clear` over a single dict stored under
one key, scoped to a `(principal, session_id)` pair. This is the state-accessor
object a handler works with — the value the standalone `get_session(id)`
returns and the value injected for a `UserSession` parameter.
- `session: UserSession` (injected): a per-user bucket, dependency-injected like
`ctx: Context` and keyed by the request's authenticated principal. Requires
auth. `UserSession` is the injection annotation; the injected value is a
`Session`. It is always available under auth — no `create_session`, no
provider, no validation.
- `session_id: SessionId` (argument): a required string the agent supplies,
resolved with the standalone `await get_session(session_id)`. The id is
minted
by `create_session`; an id that was never created (or was created under a
different principal) is rejected. This validation is the whole guarantee — an
unminted id never resolves, so nothing enforces provider registration.
- `SessionProvider`: a `Provider` contributing `create_session` / `end_session`
tools. Register it with `mcp.add_provider(SessionProvider())` so a tool that
takes `session_id` has a way to mint ids; without it, no id can be created, so
those tools simply cannot resolve a session.
Isolation is the authenticated principal, not the session id. State keyed by
`(principal, session_id)` means a request under principal B can never address
principal A's keys, no matter what `session_id` it passes; the id only organizes
sessions within a principal. Without auth there is no principal wall — a session
id is a bearer capability and sessions are not a boundary between clients.
## Functions
### `current_principal` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L139" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
current_principal() -> str | None
```
The authenticated principal for the current request as a compact JSON string.
Returns the `(client_id, issuer, subject)` triple encoded as compact JSON, or
`None` on an unauthenticated request. Two users of one OAuth client are
distinct principals whenever the token verifier supplies a subject.
### `session_storage_key` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L164" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
session_storage_key(principal: str | None, session_id: str) -> str
```
The single storage key holding a session's state dict.
Keyed by `(principal, session_id)`: the principal is the isolation wall, the
id organizes sessions within it. A session's whole state lives under this one
key as a dict, so one key means one store TTL per session and `end` is a
single delete.
### `session_id_parameter_names` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L343" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
session_id_parameter_names(fn: Callable[..., object]) -> tuple[str, ...]
```
Names of a function's parameters annotated with `SessionId`.
Scans resolved type hints for `Annotated[str, _SessionIdMarker()]` metadata.
Returns an empty tuple when the hints cannot be resolved (the function then
simply carries no auto-populated session-id description).
`functools.partial` is unwrapped first, since `get_type_hints` rejects a
partial object — FastMCP supports registering a partial as a tool, and its
schema is still built from the underlying function, so its `SessionId`
parameters must be detected here too. Parameters the partial has already
bound — positionally or by keyword — are dropped, matching the tool's actual
argument surface (the partial's own signature already reflects this).
### `CurrentSession` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L449" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
CurrentSession() -> Session
```
Inject the per-user `Session` for the current authenticated principal.
Rarely written explicitly — a `session: UserSession` parameter is rewritten
to this. Provided for parity with `CurrentContext()` when an explicit default
is preferred.
### `OptionalCurrentSession` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L459" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
OptionalCurrentSession() -> Session | None
```
Inject the per-user `Session`, or `None` when the request is unauthenticated.
Rarely written explicitly — a `session: UserSession | None = None` parameter
is rewritten to this. Provided for parity with `OptionalCurrentContext()`.
### `create_session` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L468" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
create_session() -> str
```
Create a new session and return its identifier.
Mints an unguessable `uuid4`, records an initial session owned by the current
principal, and returns the id as a string. Store it and pass it back as a
`session_id` argument on later calls to persist state across a session — only
an id created this way resolves. State is keyed by the authenticated
principal, so the id organizes sessions within a user; on an unauthenticated
connection the id is the only thing standing between callers, which is why it
is unguessable.
### `end_session` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L490" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
end_session(session_id: SessionId) -> str
```
End a session and delete all of its state.
Validates the id like any other resolution (an unknown or foreign id is
rejected), then deletes the session's key so the id no longer resolves.
## Classes
### `SessionAuthError` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L106" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
An injected `session: UserSession` was requested with no authenticated principal.
Per-user session injection keys off the request's authenticated principal, so
it is only meaningful under auth. A tool that needs cross-call state without
auth should take a `session_id: SessionId` argument instead.
### `InvalidSession` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L125" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
A session id did not resolve to a session created under the current principal.
Raised by `get_session(session_id)` when the id was never created, or was
created under a different principal. The public message is deliberately
generic — the specific reason (which id, which principal) is logged at debug
level, not returned to the caller, so an attacker cannot distinguish "unknown
id" from "belongs to someone else".
### `Session` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L175" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Async accessors over one `(principal, session_id)` bucket of state.
A session's state is a single dict stored under one key. That dict holds user
state in a `state` sub-dict and a small creation marker alongside it, so a
created-but-empty session is still distinguishable from a missing one.
`get`/`set`/`delete` read-modify-write the sub-dict; `clear` empties the
sub-dict but keeps the session valid; `end` deletes the whole key. Writes
never impose a TTL — retention is entirely the server store's (configure it on
the store you pass to `FastMCP(session_state_store=...)`).
Concurrent writes to one session race on the read-modify-write; session state
is small and typically driven serially by one agent, so this is acceptable.
**Methods:**
#### `id` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L205" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
id(self) -> str | None
```
The session's identifier, or `None` for an injected per-user session.
For a session resolved from a `session_id` argument (or minted by
`create_session`) this is that id. An injected `UserSession` has no
distinct id — its bucket is the authenticated user — so it is `None`; the
internal principal-derived key is deliberately not exposed here.
#### `get` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L254" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get(self, key: str, default: Any = None) -> Any
```
Return the value for `key`, or `default` when it is not set.
#### `set` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L259" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set(self, key: str, value: Any) -> None
```
Store `value` under `key` in this session (read-modify-write).
Preserves the creation marker: only the user-state sub-dict is touched.
#### `delete` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L270" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
delete(self, key: str) -> None
```
Remove `key` from this session, if present (preserves the marker).
#### `clear` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L281" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
clear(self) -> None
```
Empty the session's user state but keep the session valid.
The user-state sub-dict is reset to empty while the creation marker stays
in place, so a cleared session still resolves through `get_session`.
To invalidate a session entirely, use `end` (what `end_session` calls).
#### `end` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L294" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
end(self) -> None
```
Invalidate the session — delete its one key and all of its state.
After this the id no longer resolves through `get_session`. This is
what `end_session` calls; `clear` only empties state and keeps the session.
### `UserSession` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L303" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Annotation marker for the injected per-user session.
A `session: UserSession` parameter is **dependency-injected** like
`ctx: Context`: keyed by the request's authenticated principal, excluded from
the input schema, and requiring auth (it raises `SessionAuthError` with no
principal). It doubles as the injection *annotation* and the injected
type — the value a handler receives is a `UserSession`, which subclasses
`Session`, so `await session.get(...)`, `.set`, `.delete`, and `.clear` all
work exactly as on any other `Session`.
Unlike `session_id: SessionId`, the per-user bucket needs no `create_session`,
no `SessionProvider`, and no validation — it is always available under auth,
keyed directly by the caller's identity.
```python
from fastmcp.server.sessions import UserSession
@mcp.tool
async def remember(fact: str, session: UserSession) -> str:
await session.set("fact", fact)
return "noted"
```
Subclasses `Session` only so the framework's type-based injection detector can
key off it; it adds no behavior of its own.
### `SessionProvider` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/sessions.py#L501" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Provider contributing the session lifecycle tools.
Register it whenever a tool declares a `session_id: SessionId` argument:
```python
from fastmcp.server.sessions import SessionProvider
mcp.add_provider(SessionProvider())
```
It registers two tools:
- `create_session()` mints an unguessable `uuid4`, records the session, and
returns the id.
- `end_session(session_id)` invalidates that session and deletes its state.
It owns no storage (session state lives in the server's configured
`session_state_store`) and imposes no TTL (retention is the store's). It
exists to mint and end owned session ids. Registration is not enforced: with
no provider, no id can be created, so every `get_session(...)` rejects —
a `session_id` tool without a provider simply cannot resolve a session.

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@ -0,0 +1,117 @@
---
title: telemetry
sidebarTitle: telemetry
---
# `fastmcp.server.telemetry`
Server-side telemetry helpers.
## Functions
### `get_auth_span_attributes` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/telemetry.py#L43" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_auth_span_attributes() -> dict[str, str]
```
Get auth attributes for the current request, if authenticated.
### `get_session_span_attributes` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/telemetry.py#L60" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_session_span_attributes() -> dict[str, str]
```
Get session attributes for the current request.
### `get_protocol_span_attributes` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/telemetry.py#L74" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_protocol_span_attributes() -> dict[str, str]
```
Get the negotiated MCP protocol version for the current request.
Mirrors the `mcp.protocol.version` attribute the SDK's own
`OpenTelemetryMiddleware` sets — FastMCP drops that middleware to avoid a
duplicate SERVER span, so this restores the attribute on FastMCP's span.
### `record_span_exception` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/telemetry.py#L154" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
record_span_exception(span: Span, e: Exception) -> None
```
Record an exception and error status on a span.
### `seam_span` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/telemetry.py#L164" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
seam_span(method: str, server_name: str) -> Generator[Span, None, None]
```
Open the per-request SERVER span at the FastMCP middleware seam.
The span is named after the method and carries the base MCP attributes
(`mcp.method.name`, `fastmcp.server.name`, auth/session context) so
seam-only methods (`logging/setLevel`, `tasks/*`, `ping`, `initialize`, ...)
are fully attributed even though they never reach the high-level path. It is
marked with `SEAM_SPAN_MARKER` so a later `server_span` call in the
high-level path enriches this span with component attributes instead of
opening a second one. Exceptions raised anywhere below the seam — including
rejections *before* the high-level path (auth, not-found, middleware vetoes)
that would otherwise produce no SERVER span at all — are recorded here.
In `propagation_only` mode no span is opened at all — this is the one place
that has to know the difference, because the seam is where the incoming
`_meta` parent context is applied for the whole request.
### `server_span` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/telemetry.py#L224" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
server_span(name: str, method: str, server_name: str, component_type: str, component_key: str, resource_uri: str | None = None, tool_name: str | None = None, prompt_name: str | None = None) -> Generator[Span, None, None]
```
Emit or enrich a SERVER span with standard MCP attributes and auth context.
When the current active span is the request's seam span (opened by
`FastMCPServerMiddleware` and marked with `SEAM_SPAN_MARKER`), this sets the
component attributes on that span and yields it *without* starting a second
span — so failures rejected before this point and the successful high-level
call share one richly-attributed SERVER span. Otherwise (non-seam contexts,
e.g. in-process `mcp.call_tool()` calls that bypass the dispatcher) it opens a
new SERVER span as before.
Automatically records any exception on the span and sets error status.
In `propagation_only` mode no span is opened or enriched. The seam has
normally already attached the incoming parent context for this request;
doing it again here is a no-op, and covers the in-process callers that
bypass the dispatcher and so never reach the seam at all.
### `delegate_span` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/telemetry.py#L305" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
delegate_span(name: str, provider_type: str, component_key: str, method: str | None = None) -> Generator[Span, None, None]
```
Create an INTERNAL span for provider delegation.
Used by FastMCPProvider when delegating to mounted servers.
Automatically records any exception on the span and sets error status.

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@ -0,0 +1,193 @@
---
title: transforms
sidebarTitle: transforms
---
# `fastmcp.server.transforms`
Transform system for component transformations.
Transforms modify components (tools, resources, prompts). List operations use a pure
function pattern where transforms receive sequences and return transformed sequences.
Get operations use a middleware pattern with `call_next` to chain lookups.
Unlike middleware (which operates on requests), transforms are observable by the
system for task registration, tag filtering, and component introspection.
Example:
```python
from fastmcp import FastMCP
from fastmcp.server.transforms import Namespace
server = FastMCP("Server")
mount = server.mount(other_server)
mount.add_transform(Namespace("api")) # Tools become api_toolname
```
## Classes
### `GetToolNext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L36" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Protocol for get_tool call_next functions.
### `GetResourceNext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L44" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Protocol for get_resource call_next functions.
### `GetResourceTemplateNext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L52" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Protocol for get_resource_template call_next functions.
### `GetPromptNext` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L60" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Protocol for get_prompt call_next functions.
### `Transform` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L68" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Base class for component transformations.
List operations use a pure function pattern: transforms receive sequences
and return transformed sequences. Get operations use a middleware pattern
with `call_next` to chain lookups.
**Methods:**
#### `list_tools` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L95" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_tools(self, tools: Sequence[Tool]) -> Sequence[Tool]
```
List tools with transformation applied.
**Args:**
- `tools`: Sequence of tools to transform.
**Returns:**
- Transformed sequence of tools.
#### `get_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L106" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_tool(self, name: str, call_next: GetToolNext) -> Tool | None
```
Get a tool by name.
**Args:**
- `name`: The requested tool name (may be transformed).
- `call_next`: Callable to get tool from downstream.
- `version`: Optional version filter to apply.
**Returns:**
- The tool if found, None otherwise.
#### `list_resources` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L125" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_resources(self, resources: Sequence[Resource]) -> Sequence[Resource]
```
List resources with transformation applied.
**Args:**
- `resources`: Sequence of resources to transform.
**Returns:**
- Transformed sequence of resources.
#### `get_resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L136" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_resource(self, uri: str, call_next: GetResourceNext) -> Resource | None
```
Get a resource by URI.
**Args:**
- `uri`: The requested resource URI (may be transformed).
- `call_next`: Callable to get resource from downstream.
- `version`: Optional version filter to apply.
**Returns:**
- The resource if found, None otherwise.
#### `list_resource_templates` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L159" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_resource_templates(self, templates: Sequence[ResourceTemplate]) -> Sequence[ResourceTemplate]
```
List resource templates with transformation applied.
**Args:**
- `templates`: Sequence of resource templates to transform.
**Returns:**
- Transformed sequence of resource templates.
#### `get_resource_template` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L172" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_resource_template(self, uri: str, call_next: GetResourceTemplateNext) -> ResourceTemplate | None
```
Get a resource template by URI.
**Args:**
- `uri`: The requested template URI (may be transformed).
- `call_next`: Callable to get template from downstream.
- `version`: Optional version filter to apply.
**Returns:**
- The resource template if found, None otherwise.
#### `list_prompts` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L195" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
list_prompts(self, prompts: Sequence[Prompt]) -> Sequence[Prompt]
```
List prompts with transformation applied.
**Args:**
- `prompts`: Sequence of prompts to transform.
**Returns:**
- Transformed sequence of prompts.
#### `get_prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/transforms/__init__.py#L206" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_prompt(self, name: str, call_next: GetPromptNext) -> Prompt | None
```
Get a prompt by name.
**Args:**
- `name`: The requested prompt name (may be transformed).
- `call_next`: Callable to get prompt from downstream.
- `version`: Optional version filter to apply.
**Returns:**
- The prompt if found, None otherwise.

View file

@ -7,7 +7,7 @@ sidebarTitle: settings
## Classes
### `Settings` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/settings.py#L32" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `Settings` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/settings.py#L34" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
FastMCP settings.
@ -15,7 +15,7 @@ FastMCP settings.
**Methods:**
#### `get_setting` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/settings.py#L44" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `get_setting` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/settings.py#L46" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_setting(self, attr: str) -> Any
@ -25,7 +25,7 @@ Get a setting. If the setting contains one or more `__`, it will be
treated as a nested setting.
#### `set_setting` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/settings.py#L57" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `set_setting` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/settings.py#L59" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
set_setting(self, attr: str, value: Any) -> None
@ -35,7 +35,7 @@ Set a setting. If the setting contains one or more `__`, it will be
treated as a nested setting.
#### `normalize_log_level` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/settings.py#L79" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
#### `normalize_log_level` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/settings.py#L81" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
normalize_log_level(cls, v)

View file

@ -31,7 +31,52 @@ Example usage with SDK:
## Functions
### `get_tracer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L81" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `telemetry_mode` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L86" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
telemetry_mode() -> 'TelemetryMode'
```
Resolve the effective telemetry mode for the current context.
This is `fastmcp.settings.telemetry_mode`, except that an active
`suppress_fastmcp_telemetry()` block downgrades `native` to
`propagation_only`. Suppression never upgrades or overrides `off`: `off`
means FastMCP touches nothing, and a narrower request to skip FastMCP's
spans cannot re-enable the context propagation `off` deliberately omits.
### `native_spans_enabled` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L103" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
native_spans_enabled() -> bool
```
Whether FastMCP should create its own spans right now.
### `suppress_fastmcp_telemetry` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L109" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
suppress_fastmcp_telemetry() -> Iterator[None]
```
Suppress FastMCP's own spans without disabling trace propagation.
Scoped equivalent of `telemetry_mode="propagation_only"`, for callers that
embed FastMCP inside their own instrumented stack and want to own the MCP
span hierarchy for a specific block. Narrower than OpenTelemetry's global
instrumentation suppression: only FastMCP's spans are skipped, so nested
instrumentation (HTTP clients, databases) keeps emitting, and trace context
still flows through `_meta` so those spans are parented correctly.
Has no effect when `telemetry_mode` is already `off`.
### `get_tracer` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L128" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_tracer(version: str | None = None) -> Tracer
@ -42,21 +87,22 @@ Get the FastMCP tracer for creating spans.
Instrumentation is on by default. FastMCP uses only the OpenTelemetry API,
so span creation is a no-op with negligible overhead unless an OpenTelemetry
SDK and exporter are configured. Set `fastmcp.settings.enable_telemetry` to
False (env `FASTMCP_ENABLE_TELEMETRY=false`) to turn instrumentation off
entirely, in which case this returns a pass-through tracer that leaves the
current OTel context untouched even when an SDK is configured.
SDK and exporter are configured. When `fastmcp.settings.telemetry_mode` is
`propagation_only` or `off` — or the caller is inside a
`suppress_fastmcp_telemetry()` block — this returns a pass-through tracer
that creates no spans and leaves the current OTel context untouched even
when an SDK is configured.
**Args:**
- `version`: Optional version string for the instrumentation
**Returns:**
- A tracer instance. Returns a non-attaching pass-through tracer if
- telemetry is disabled; span creation is otherwise a no-op unless an SDK
- is configured.
- A tracer instance. Returns a non-attaching pass-through tracer when
- FastMCP's own spans are disabled; span creation is otherwise a no-op
- unless an SDK is configured.
### `inject_trace_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L106" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `inject_trace_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L152" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
inject_trace_context(meta: dict[str, Any] | None = None) -> dict[str, Any] | None
@ -73,7 +119,7 @@ Inject current trace context into a meta dict for MCP request propagation.
- or None if no trace context to inject and meta was None
### `record_span_error` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L132" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `record_span_error` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L183" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
record_span_error(span: Span, exception: BaseException) -> None
@ -83,7 +129,7 @@ record_span_error(span: Span, exception: BaseException) -> None
Record an exception on a span and set error status.
### `restore_dropped_attributes` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L158" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `restore_dropped_attributes` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L209" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
restore_dropped_attributes(span: Span, attrs: Mapping[str, otel_types.AttributeValue]) -> None
@ -133,7 +179,7 @@ kept at call sites so it reads alongside the sibling `is_recording()`
guards already in those functions.
### `extract_trace_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L212" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `extract_trace_context` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/telemetry.py#L263" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
extract_trace_context(meta: dict[str, Any] | None) -> Context

View file

@ -16,7 +16,7 @@ callers.
## Functions
### `parse_docstring` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/docstring_parsing.py#L35" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `parse_docstring` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/docstring_parsing.py#L33" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
parse_docstring(fn: Callable[..., Any]) -> ParsedDocstring
@ -32,7 +32,7 @@ docstring as the description with no parameter descriptions.
## Classes
### `ParsedDocstring` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/docstring_parsing.py#L28" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `ParsedDocstring` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/docstring_parsing.py#L26" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
The extracted description and per-parameter descriptions from a docstring.

View file

@ -7,13 +7,53 @@ sidebarTitle: exceptions
## Functions
### `iter_exc` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/exceptions.py#L36" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `is_http_status_error` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/exceptions.py#L19" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_http_status_error(exc: BaseException) -> bool
```
Return whether an exception is an httpx2 or legacy-httpx status error.
### `get_http_status_code` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/exceptions.py#L26" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_http_status_code(exc: BaseException) -> int | None
```
Return the response status code from a recognized HTTP status error.
### `is_timeout_error` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/exceptions.py#L34" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_timeout_error(exc: BaseException) -> bool
```
Return whether an exception is an httpx2 or legacy-httpx timeout.
### `is_request_error` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/exceptions.py#L41" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_request_error(exc: BaseException) -> bool
```
Return whether an exception is an httpx2 or legacy-httpx request error.
### `iter_exc` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/exceptions.py#L48" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
iter_exc(group: BaseExceptionGroup)
```
### `get_catch_handlers` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/exceptions.py#L64" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `get_catch_handlers` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/exceptions.py#L76" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_catch_handlers() -> Mapping[type[BaseException] | Iterable[type[BaseException]], Callable[[BaseExceptionGroup[Any]], Any]]

View file

@ -42,7 +42,7 @@ Extract information from a FastMCP v1.x instance using a Client.
- FastMCPInfo dataclass containing the extracted information
### `inspect_fastmcp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L411" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `inspect_fastmcp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L413" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
inspect_fastmcp(mcp: FastMCP[Any] | SDKServer) -> FastMCPInfo
@ -61,7 +61,7 @@ and uses the appropriate extraction method.
- FastMCPInfo dataclass containing the extracted information
### `format_fastmcp_info` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L436" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `format_fastmcp_info` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L438" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
format_fastmcp_info(info: FastMCPInfo) -> bytes
@ -73,7 +73,7 @@ Format FastMCPInfo as FastMCP-specific JSON.
This includes FastMCP-specific fields like tags, enabled, annotations, etc.
### `format_mcp_info` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L465" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `format_mcp_info` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L467" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
format_mcp_info(mcp: FastMCP[Any] | SDKServer) -> bytes
@ -86,7 +86,7 @@ Uses Client to get the standard MCP protocol format with camelCase fields.
Includes version metadata at the top level.
### `format_info` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L500" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `format_info` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L502" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
format_info(mcp: FastMCP[Any] | SDKServer, format: InspectFormat | Literal['fastmcp', 'mcp'], info: FastMCPInfo | None = None) -> bytes
@ -136,7 +136,7 @@ Information about a resource template.
Information extracted from a FastMCP instance.
### `InspectFormat` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L429" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `InspectFormat` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/inspect.py#L431" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
Output format for inspect command.

View file

@ -7,7 +7,17 @@ sidebarTitle: json_schema
## Functions
### `require_discriminator_property` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L149" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `replace_refs` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L7" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
replace_refs(*args: Any, **kwargs: Any) -> Any
```
Call jsonref lazily while preserving the module's patchable boundary.
### `require_discriminator_property` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L154" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
require_discriminator_property(schema: dict[str, Any]) -> dict[str, Any]
@ -24,7 +34,7 @@ model with ``union_tag_not_found``. No-op if there is no string
``propertyName``.
### `dereference_refs` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L180" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `dereference_refs` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L185" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
dereference_refs(schema: dict[str, Any]) -> dict[str, Any]
@ -57,7 +67,7 @@ schemas from untrusted servers.
- when no longer needed
### `resolve_root_ref` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L327" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `resolve_root_ref` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L336" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
resolve_root_ref(schema: dict[str, Any]) -> dict[str, Any]
@ -79,7 +89,7 @@ the referenced definition while preserving $defs for nested references.
- if no resolution is needed
### `compress_schema` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L741" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `compress_schema` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/json_schema.py#L750" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
compress_schema(schema: dict[str, Any], prune_params: list[str] | None = None, prune_additional_properties: bool = False, prune_titles: bool = False, dereference: bool = False) -> dict[str, Any]

View file

@ -10,7 +10,7 @@ Logging utilities for FastMCP.
## Functions
### `get_logger` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/logging.py#L14" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `get_logger` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/logging.py#L27" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
get_logger(name: str) -> logging.Logger
@ -26,7 +26,7 @@ Get a logger nested under FastMCP namespace.
- a configured logger instance
### `configure_logging` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/logging.py#L29" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `configure_logging` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/logging.py#L42" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
configure_logging(level: Literal['DEBUG', 'INFO', 'WARNING', 'ERROR', 'CRITICAL'] | int = 'INFO', logger: logging.Logger | None = None, enable_rich_tracebacks: bool | None = None, **rich_kwargs: Any) -> None
@ -41,7 +41,7 @@ Configure logging for FastMCP.
- `rich_kwargs`: the parameters to use for creating RichHandler
### `temporary_log_level` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/logging.py#L117" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
### `temporary_log_level` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/logging.py#L127" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
temporary_log_level(level: str | None, logger: logging.Logger | None = None, enable_rich_tracebacks: bool | None = None, **rich_kwargs: Any)

View file

@ -0,0 +1,61 @@
---
title: prefab
sidebarTitle: prefab
---
# `fastmcp.utilities.prefab`
Lazy helpers for FastMCP's optional Prefab UI integration.
## Functions
### `prefab_available` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/prefab.py#L12" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
prefab_available() -> bool
```
Return whether Prefab UI is installed without importing it.
### `is_prefab_type` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/prefab.py#L42" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_prefab_type(candidate: Any) -> bool
```
Return whether a type is a Prefab app or component type.
### `is_prefab_app` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/prefab.py#L51" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_prefab_app(value: Any) -> bool
```
Return whether a value is a Prefab app.
### `is_prefab_component` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/prefab.py#L60" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
is_prefab_component(value: Any) -> bool
```
Return whether a value is a Prefab component.
### `prefab_app_from_component` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/utilities/prefab.py#L69" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
prefab_app_from_component(component: Any) -> Any
```
Wrap a Prefab component in a Prefab app.