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f6988c9206Co-authored-by: marvin-context-protocol[bot] <225465937+marvin-context-protocol[bot]@users.noreply.github.com>
87 lines
3.1 KiB
Text
87 lines
3.1 KiB
Text
---
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title: apps
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sidebarTitle: apps
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---
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# `fastmcp.server.apps`
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MCP Apps support — extension negotiation and typed UI metadata models.
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Provides constants and Pydantic models for the MCP Apps extension
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(io.modelcontextprotocol/ui), enabling tools and resources to carry
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UI metadata for clients that support interactive app rendering.
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## Functions
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### `ui_to_meta_dict` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/apps.py#L129" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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ui_to_meta_dict(ui: ToolUI | ResourceUI | dict[str, Any]) -> dict[str, Any]
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```
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Convert a UI model or dict to the wire-format dict for ``meta["ui"]``.
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### `resolve_ui_mime_type` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/apps.py#L136" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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```python
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resolve_ui_mime_type(uri: str, explicit_mime_type: str | None) -> str | None
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```
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Return the appropriate MIME type for a resource URI.
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For ``ui://`` scheme resources, defaults to ``UI_MIME_TYPE`` when no
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explicit MIME type is provided. This ensures UI resources are correctly
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identified regardless of how they're registered (via FastMCP.resource,
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the standalone @resource decorator, or resource templates).
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**Args:**
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- `uri`: The resource URI string
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- `explicit_mime_type`: The MIME type explicitly provided by the user
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**Returns:**
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- The resolved MIME type (explicit value, UI default, or None)
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## Classes
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### `ResourceCSP` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/apps.py#L18" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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Content Security Policy for MCP App resources.
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Declares which external origins the app is allowed to connect to or
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load resources from. Hosts use these declarations to build the
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``Content-Security-Policy`` header for the sandboxed iframe.
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### `ResourcePermissions` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/apps.py#L50" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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Iframe sandbox permissions for MCP App resources.
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Each field, when set (typically to ``{}``), requests that the host
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grant the corresponding Permission Policy feature to the sandboxed
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iframe. Hosts MAY honour these; apps should use JS feature detection
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as a fallback.
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### `ToolUI` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/apps.py#L77" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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Typed ``_meta.ui`` for tools — links a tool to its UI resource.
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All fields use ``exclude_none`` serialization so only explicitly-set
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values appear on the wire. Aliases match the MCP Apps wire format
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(camelCase).
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### `ResourceUI` <sup><a href="https://github.com/jlowin/fastmcp/blob/main/src/fastmcp/server/apps.py#L110" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a></sup>
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Typed ``_meta.ui`` for resources — rendering hints for UI-capable clients.
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