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2c451bf6baCo-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
163 lines
5.2 KiB
Text
163 lines
5.2 KiB
Text
---
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title: app
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sidebarTitle: app
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---
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# `fastmcp.server.app`
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FastMCPApp — a Provider that represents a composable MCP application.
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FastMCPApp binds entry-point tools (model calls these) together with backend
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tools (the UI calls these via CallTool). Backend tools get global keys —
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UUID-suffixed stable identifiers that survive namespace transforms when
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servers are composed — so ``CallTool(save_contact)`` keeps working even when
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the app is mounted under a namespace.
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Usage::
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from fastmcp import FastMCP, FastMCPApp
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app = FastMCPApp("Dashboard")
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@app.ui()
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def show_dashboard() -> Component:
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return Column(...)
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@app.tool()
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def save_contact(name: str, email: str) -> dict:
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return {"name": name, "email": email}
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server = FastMCP("Platform")
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server.add_provider(app)
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## Functions
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### `get_global_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L61" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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get_global_tool(name: str) -> Tool | None
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```
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Look up a tool by its global key, or return None.
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## Classes
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### `FastMCPApp` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L167" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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A Provider that represents an MCP application.
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Binds together entry-point tools (``@app.ui``), backend tools
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(``@app.tool``), the Prefab renderer resource, and global-key
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infrastructure so that composed/namespaced servers can still reach
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backend tools by stable identifiers.
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**Methods:**
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#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L189" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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tool(self, name_or_fn: F) -> F
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```
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#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L201" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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tool(self, name_or_fn: str | None = None) -> Callable[[F], F]
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```
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#### `tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L212" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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tool(self, name_or_fn: str | AnyFunction | None = None) -> Any
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```
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Register a backend tool that the UI calls via CallTool.
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Backend tools get a global key for composition safety and default
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to ``visibility=["app"]``. Pass ``model=True`` to also expose the
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tool to the model (``visibility=["app", "model"]``).
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Supports multiple calling patterns::
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@app.tool
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def save(name: str): ...
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@app.tool()
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def save(name: str): ...
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@app.tool("custom_name")
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def save(name: str): ...
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#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L274" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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ui(self, name_or_fn: F) -> F
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```
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#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L289" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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ui(self, name_or_fn: str | None = None) -> Callable[[F], F]
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```
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#### `ui` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L303" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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ui(self, name_or_fn: str | AnyFunction | None = None) -> Any
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```
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Register a UI entry-point tool that the model calls.
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Entry-point tools default to ``visibility=["model"]`` and auto-wire
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the Prefab renderer resource and CSP. They do NOT get a global key —
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the model resolves them through the normal transform chain.
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Supports multiple calling patterns::
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@app.ui
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def dashboard() -> Component: ...
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@app.ui()
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def dashboard() -> Component: ...
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@app.ui("my_dashboard")
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def dashboard() -> Component: ...
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#### `add_tool` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L389" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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add_tool(self, tool: Tool | Callable[..., Any]) -> Tool
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```
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Add a tool to this app programmatically.
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If the tool has ``meta["ui"]["globalKey"]``, it is assumed to already
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be configured (but still registered for lookup). Otherwise it is
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treated as a backend tool and gets a global key assigned automatically.
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Pass ``fn`` to register the original callable in the resolver so that
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``CallTool(fn)`` can resolve to the global key.
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#### `lifespan` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L453" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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lifespan(self) -> AsyncIterator[None]
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```
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#### `run` <sup><a href="https://github.com/PrefectHQ/fastmcp/blob/main/src/fastmcp/server/app.py#L461" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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run(self, transport: Literal['stdio', 'http', 'sse', 'streamable-http'] | None = None, **kwargs: Any) -> None
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```
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Create a temporary FastMCP server and run this app standalone.
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