fastmcp_provider

fastmcp.server.providers.fastmcp_provider

FastMCPProvider for wrapping FastMCP servers as providers.

This module provides the FastMCPProvider class that wraps a FastMCP server and exposes its components through the Provider interface.

It also provides FastMCPProvider* component classes that delegate execution to the wrapped server’s middleware, ensuring middleware runs when components are executed.

Classes

FastMCPProviderTool

Tool that delegates execution to a wrapped server’s middleware.

When run() is called, this tool invokes the wrapped server’s _call_tool_middleware() method, ensuring the server’s middleware chain is executed.

Methods:

wrap

wrap(cls, server: Any, tool: Tool) -> FastMCPProviderTool

Wrap a Tool to delegate execution to the server’s middleware.

run

run(self, arguments: dict[str, Any]) -> ToolResult

Delegate to child server’s call_tool() without task_meta.

This is called when the tool is used within a TransformedTool forwarding function or other contexts where task_meta is not available.

get_span_attributes

get_span_attributes(self) -> dict[str, Any]

FastMCPProviderResource

Resource that delegates reading to a wrapped server’s read_resource().

When read() is called, this resource invokes the wrapped server’s read_resource() method, ensuring the server’s middleware chain is executed.

Methods:

wrap

wrap(cls, server: Any, resource: Resource) -> FastMCPProviderResource

Wrap a Resource to delegate reading to the server’s middleware.

get_span_attributes

get_span_attributes(self) -> dict[str, Any]

FastMCPProviderPrompt

Prompt that delegates rendering to a wrapped server’s render_prompt().

When render() is called, this prompt invokes the wrapped server’s render_prompt() method, ensuring the server’s middleware chain is executed.

Methods:

wrap

wrap(cls, server: Any, prompt: Prompt) -> FastMCPProviderPrompt

Wrap a Prompt to delegate rendering to the server’s middleware.

render

render(self, arguments: dict[str, Any] | None = None) -> PromptResult

Delegate to child server’s render_prompt() without task_meta.

This is called when the prompt is used within a transformed context or other contexts where task_meta is not available.

get_span_attributes

get_span_attributes(self) -> dict[str, Any]

FastMCPProviderResourceTemplate

Resource template that creates FastMCPProviderResources.

When create_resource() is called, this template creates a FastMCPProviderResource that will invoke the wrapped server’s middleware when read.

Methods:

wrap

wrap(cls, server: Any, template: ResourceTemplate) -> FastMCPProviderResourceTemplate

Wrap a ResourceTemplate to create FastMCPProviderResources.

create_resource

create_resource(self, uri: str, params: dict[str, Any]) -> Resource

Create a FastMCPProviderResource for the given URI.

The uri is the external/transformed URI (e.g., with namespace prefix). We use _original_uri_template with params to construct the internal URI that the nested server understands.

read

read(self, arguments: dict[str, Any]) -> str | bytes | ResourceResult

Read the resource content for background task execution.

Reads the resource via the wrapped server and returns the ResourceResult. This method is called by Docket during background task execution.

register_with_docket

register_with_docket(self, docket: Docket) -> None

No-op: the child’s actual template is registered via get_tasks().

add_to_docket

add_to_docket(self, docket: Docket, params: dict[str, Any], **kwargs: Any) -> Execution

Schedule this template for background execution via docket.

The child’s FunctionResourceTemplate.fn is registered (via get_tasks), and it expects splatted **kwargs, so we splat params here.

get_span_attributes

get_span_attributes(self) -> dict[str, Any]

FastMCPProvider

Provider that wraps a FastMCP server.

This provider enables mounting one FastMCP server onto another, exposing the mounted server’s tools, resources, and prompts through the parent server.

Components returned by this provider are wrapped in FastMCPProvider* classes that delegate execution to the wrapped server’s middleware chain. This ensures middleware runs when components are executed.

Methods:

get_tasks

get_tasks(self) -> Sequence[FastMCPComponent]

Return task-eligible components from the mounted server.

Returns the child’s ACTUAL components (not wrapped) so their actual functions get registered with Docket. Gets components with child server’s transforms applied, then applies this provider’s transforms for correct registration keys.

lifespan

lifespan(self) -> AsyncIterator[None]

Start the mounted server’s user lifespan.

This starts only the wrapped server’s user-defined lifespan, NOT its full _lifespan_manager() (which includes Docket). The parent server’s Docket handles all background tasks.