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fastmcp.resources.function_resource

Standalone @resource decorator for FastMCP.

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Functions

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resource 

resource(uri: str) -> Callable[[F], F]
Standalone decorator to mark a function as an MCP resource. Returns the original function with metadata attached. Register with a server using mcp.add_resource().

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Classes

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DecoratedResource

Protocol for functions decorated with @resource.

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ResourceMeta

Metadata attached to functions by the @resource decorator.

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FunctionResource

A resource that defers data loading by wrapping a function. The function is only called when the resource is read, allowing for lazy loading of potentially expensive data. This is particularly useful when listing resources, as the function won’t be called until the resource is actually accessed. The function can return:
  • str for text content (default)
  • bytes for binary content
  • other types will be converted to JSON
Methods:

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from_function 

from_function(cls, fn: Callable[..., Any], uri: str | AnyUrl | None = None) -> FunctionResource
Create a FunctionResource from a function. Args:
  • fn: The function to wrap
  • uri: The URI for the resource (required if metadata not provided)
  • metadata: ResourceMeta object with all configuration. If provided, individual parameters must not be passed.
  • name, title, etc.: Individual parameters for backwards compatibility. Cannot be used together with metadata parameter.

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read 

read(self) -> str | bytes | ResourceResult
Read the resource by calling the wrapped function.

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register_with_docket 

register_with_docket(self, docket: Docket) -> None
Register this resource with docket for background execution. FunctionResource registers the underlying function, which has the user’s Depends parameters for docket to resolve.