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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/src/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/src/fastmcp/server/server.py#L2415" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
create_proxy(target: Client[ClientTransportT] | ClientTransport | FastMCP[Any] | FastMCP1Server | 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
- `**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/src/fastmcp/server/server.py#L273" 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/src/fastmcp/server/server.py#L279" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
**Methods:**
#### `name` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L434" 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/src/fastmcp/server/server.py#L438" 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/src/fastmcp/server/server.py#L442" 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/src/fastmcp/server/server.py#L446" 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/src/fastmcp/server/server.py#L450" 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/src/fastmcp/server/server.py#L454" 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/src/fastmcp/server/server.py#L461" 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/src/fastmcp/server/server.py#L483" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_middleware(self, middleware: Middleware) -> None
```
#### `add_provider` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L486" 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/src/fastmcp/server/server.py#L526" 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/src/fastmcp/server/server.py#L555" 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.
#### `add_tool_transformation` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L575" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
add_tool_transformation(self, tool_name: str, transformation: ToolTransformConfig) -> None
```
Add a tool transformation.
.. deprecated::
Use ``add_transform(ToolTransform({...}))`` instead.
#### `remove_tool_transformation` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L592" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
remove_tool_transformation(self, _tool_name: str) -> None
```
Remove a tool transformation.
.. deprecated::
Tool transformations are now immutable. Use enable/disable controls instead.
#### `list_tools` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L607" 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 visibility 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/src/fastmcp/server/server.py#L687" 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 add visibility filtering 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/src/fastmcp/server/server.py#L741" 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/src/fastmcp/server/server.py#L826" 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/src/fastmcp/server/server.py#L876" 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/src/fastmcp/server/server.py#L958" 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/src/fastmcp/server/server.py#L1012" 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/src/fastmcp/server/server.py#L1084" 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/src/fastmcp/server/server.py#L1135" 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_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L1146" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
call_tool(self, name: str, arguments: dict[str, Any] | None = None) -> mcp.types.CreateTaskResult
```
#### `call_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L1156" 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 | mcp.types.CreateTaskResult
```
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.
- `task_meta`: If provided, execute as a background task and return
CreateTaskResult. If None (default), execute synchronously and
return ToolResult.
**Returns:**
- ToolResult when task_meta is None.
- CreateTaskResult when task_meta is provided.
**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/src/fastmcp/server/server.py#L1294" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
read_resource(self, uri: str) -> ResourceResult
```
#### `read_resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L1304" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
read_resource(self, uri: str) -> mcp.types.CreateTaskResult
```
#### `read_resource` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L1313" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
read_resource(self, uri: str) -> ResourceResult | mcp.types.CreateTaskResult
```
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.
- `task_meta`: If provided, execute as a background task and return
CreateTaskResult. If None (default), execute synchronously and
return ResourceResult.
**Returns:**
- ResourceResult when task_meta is None.
- CreateTaskResult when task_meta is provided.
**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/src/fastmcp/server/server.py#L1471" 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_prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L1482" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
render_prompt(self, name: str, arguments: dict[str, Any] | None = None) -> mcp.types.CreateTaskResult
```
#### `render_prompt` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L1492" 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 | mcp.types.CreateTaskResult
```
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.
- `task_meta`: If provided, execute as a background task and return
CreateTaskResult. If None (default), execute synchronously and
return PromptResult.
**Returns:**
- PromptResult when task_meta is None.
- CreateTaskResult when task_meta is provided.
**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/src/fastmcp/server/server.py#L1578" 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.
#### `remove_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L1592" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
remove_tool(self, name: str, version: str | None = None) -> None
```
Remove tool(s) from the server.
.. deprecated::
Use ``mcp.local_provider.remove_tool(name)`` instead.
**Args:**
- `name`: The name of the tool to remove.
- `version`: If None, removes ALL versions. If specified, removes only that version.
**Raises:**
- `NotFoundError`: If no matching tool is found.
#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L1622" 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/src/fastmcp/server/server.py#L1644" 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/src/fastmcp/server/server.py#L1665" 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
- `exclude_args`: Optional list of argument names to exclude from the tool schema.
Deprecated\: Use `Depends()` for dependency injection instead.
- `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/src/fastmcp/server/server.py#L1766" 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/src/fastmcp/server/server.py#L1779" 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/src/fastmcp/server/server.py#L1790" 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/src/fastmcp/server/server.py#L1909" 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/src/fastmcp/server/server.py#L1921" 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/src/fastmcp/server/server.py#L1937" 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/src/fastmcp/server/server.py#L1952" 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")
```
#### `mount` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L2052" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
mount(self, server: FastMCP[LifespanResultT], namespace: str | None = None, as_proxy: bool | None = None, tool_names: dict[str, str] | None = None, prefix: str | None = None) -> None
```
Mount another FastMCP server on this server with an optional namespace.
Unlike importing (with import_server), 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.
- `as_proxy`: Deprecated. Mounted servers now always have their lifespan and
middleware invoked. To create a proxy server, use create_proxy()
explicitly before mounting.
- `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.
- `prefix`: Deprecated. Use namespace instead.
#### `import_server` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L2158" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
import_server(self, server: FastMCP[LifespanResultT], prefix: str | None = None) -> None
```
Import the MCP objects from another FastMCP server into this one,
optionally with a given prefix.
.. deprecated::
Use :meth:`mount` instead. ``import_server`` will be removed in a
future version.
Note that when a server is *imported*, its objects are immediately
registered to the importing server. This is a one-time operation and
future changes to the imported server will not be reflected in the
importing server. Server-level configurations and lifespans are not imported.
When a server is imported with a prefix:
- The tools are imported with prefixed names
Example: If server has a tool named "get_weather", it will be
available as "prefix_get_weather"
- The resources are imported with prefixed URIs using the new format
Example: If server has a resource with URI "weather://forecast", it will
be available as "weather://prefix/forecast"
- The templates are imported with prefixed URI templates using the new format
Example: If server has a template with URI "weather://location/{id}", it will
be available as "weather://prefix/location/{id}"
- The prompts are imported with prefixed names
Example: If server has a prompt named "weather_prompt", it will be available as
"prefix_weather_prompt"
When a server is imported without a prefix (prefix=None), its tools, resources,
templates, and prompts are imported with their original names.
**Args:**
- `server`: The FastMCP server to import
- `prefix`: Optional prefix to use for the imported server's objects. If None,
objects are imported with their original names.
#### `from_openapi` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L2258" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
from_openapi(cls, openapi_spec: dict[str, Any], client: httpx.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 httpx 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.
- `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/src/fastmcp/server/server.py#L2309" 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 httpx.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.
#### `as_proxy` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L2364" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
as_proxy(cls, backend: Client[ClientTransportT] | ClientTransport | FastMCP[Any] | FastMCP1Server | AnyUrl | Path | MCPConfig | dict[str, Any] | str, **settings: Any) -> FastMCPProxy
```
Create a FastMCP proxy server for the given backend.
.. deprecated::
Use :func:`fastmcp.server.create_proxy` instead.
This method will be removed in a future version.
The `backend` argument can be either an existing `fastmcp.client.Client`
instance or any value accepted as the `transport` argument of
`fastmcp.client.Client`. This mirrors the convenience of the
`fastmcp.client.Client` constructor.
#### `generate_name` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/server.py#L2401" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
```python
generate_name(cls, name: str | None = None) -> str
```