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fastmcp.server.context

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Functions

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set_context

set_context(context: Context) -> Generator[Context, None, None]

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Classes

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Context

Context object providing access to MCP capabilities.

This provides a cleaner interface to MCP’s RequestContext functionality. It gets injected into tool and resource functions that request it via type hints.

To use context in a tool function, add a parameter with the Context type annotation:

@server.tool
def my_tool(x: int, ctx: Context) -> str:
    # Log messages to the client
    ctx.info(f"Processing {x}")
    ctx.debug("Debug info")
    ctx.warning("Warning message")
    ctx.error("Error message")

    # Report progress
    ctx.report_progress(50, 100, "Processing")

    # Access resources
    data = ctx.read_resource("resource://data")

    # Get request info
    request_id = ctx.request_id
    client_id = ctx.client_id

    return str(x)

The context parameter name can be anything as long as it’s annotated with Context. The context is optional - tools that don’t need it can omit the parameter.

Methods:

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request_context

request_context(self) -> RequestContext

Access to the underlying request context.

If called outside of a request context, this will raise a ValueError.

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client_id

client_id(self) -> str | None

Get the client ID if available.

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request_id

request_id(self) -> str

Get the unique ID for this request.

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session_id

session_id(self) -> str | None

Get the MCP session ID for HTTP transports.

Returns the session ID that can be used as a key for session-based data storage (e.g., Redis) to share data between tool calls within the same client session.

Returns:

• The session ID for HTTP transports (SSE, StreamableHTTP), or None
• for stdio and in-memory transports which don’t use session IDs.

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session

session(self)

Access to the underlying session for advanced usage.

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get_http_request

get_http_request(self) -> Request

Get the active starlette request.