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146 lines
4.7 KiB
Text
146 lines
4.7 KiB
Text
---
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title: app
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sidebarTitle: app
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---
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# `fastmcp.apps.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 are tagged with
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``meta["fastmcp"]["app"]`` so they can be found through the provider chain
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even when transforms (namespace, visibility, etc.) have renamed or hidden
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them — the server sets a context var that tells ``Provider.get_tool`` to
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fall back to a direct lookup for app-visible tools.
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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) -> str:
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return name
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server = FastMCP("Platform")
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server.add_provider(app)
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## Classes
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### `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>
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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``), and the Prefab renderer resource. Backend tools
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are tagged with ``meta["fastmcp"]["app"]`` so ``Provider.get_tool``
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can find them by original name even when transforms have been applied.
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**Methods:**
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#### `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>
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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/fastmcp_slim/fastmcp/apps/app.py#L181" 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/fastmcp_slim/fastmcp/apps/app.py#L192" 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 default to ``visibility=["app"]``. Pass ``model=True``
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to also expose the 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/fastmcp_slim/fastmcp/apps/app.py#L259" 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/fastmcp_slim/fastmcp/apps/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: 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/fastmcp_slim/fastmcp/apps/app.py#L288" 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 are tagged with the app
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name so structured content includes ``_meta.fastmcp.app``.
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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/fastmcp_slim/fastmcp/apps/app.py#L363" 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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The tool is tagged with this app's name for routing.
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#### `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>
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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/fastmcp_slim/fastmcp/apps/app.py#L427" 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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