fastmcp.server.http

Functions

set_http_request ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L355" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

set_http_request(request: Request) -> Generator[Request, None, None]

create_base_app ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L388" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

create_base_app(routes: list[BaseRoute], middleware: list[Middleware], debug: bool = False, lifespan: Callable | None = None) -> StarletteWithLifespan

Create a base Starlette app with common middleware and routes.

Args:

• routes: List of routes to include in the app
• middleware: List of middleware to include in the app
• debug: Whether to enable debug mode
• lifespan: Optional lifespan manager for the app

Returns:

• A Starlette application

create_sse_app ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L416" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

create_sse_app(server: FastMCP[LifespanResultT], message_path: str, sse_path: str, auth: AuthProvider | None = None, debug: bool = False, routes: list[BaseRoute] | None = None, middleware: list[Middleware] | None = None) -> StarletteWithLifespan

Return an instance of the SSE server app.

Args:

• server: The FastMCP server instance
• message_path: Path for SSE messages
• sse_path: Path for SSE connections
• auth: Optional authentication provider (AuthProvider)
• debug: Whether to enable debug mode
• routes: Optional list of custom routes
• middleware: Optional list of middleware

Returns: A Starlette application with RequestContextMiddleware

create_streamable_http_app ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L545" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

create_streamable_http_app(server: FastMCP[LifespanResultT], streamable_http_path: str, event_store: EventStore | None = None, retry_interval: int | None = None, auth: AuthProvider | None = None, json_response: bool = False, stateless_http: bool = False, debug: bool = False, routes: list[BaseRoute] | None = None, middleware: list[Middleware] | None = None, host_origin_protection: HostOriginProtection = False, allowed_hosts: Sequence[str] | None = None, allowed_origins: Sequence[str] | None = None, session_idle_timeout: float | None = None) -> StarletteWithLifespan

Return an instance of the StreamableHTTP server app.

Args:

• server: The FastMCP server instance
• streamable_http_path: Path for StreamableHTTP connections
• event_store: Optional event store for SSE polling/resumability
• retry_interval: Optional retry interval in milliseconds for SSE polling. Controls how quickly clients should reconnect after server-initiated disconnections. Requires event_store to be set. Defaults to SDK default.
• auth: Optional authentication provider (AuthProvider)
• json_response: Whether to use JSON response format
• stateless_http: Whether to use stateless mode (new transport per request)
• debug: Whether to enable debug mode
• routes: Optional list of custom routes
• middleware: Optional list of middleware
• host_origin_protection: Whether to validate Host and Origin headers before requests reach the MCP endpoint. Defaults to False for compatibility. "auto" protects localhost-bound servers and explicit host/origin allowlists.
• allowed_hosts: Additional hostnames that may appear in the Host header.
• allowed_origins: Additional browser origins trusted by the request guard. Configure CORS separately when browser JavaScript must read cross-origin responses.
• session_idle_timeout: Maximum time in seconds a session may remain idle before it is terminated. The deadline is pushed forward on every request. When None, sessions never expire from inactivity. Not supported in stateless mode.

Returns:

• A Starlette application with StreamableHTTP support

Classes

FastMCPStreamableHTTPSessionManager ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L43" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Session manager that scopes resumability storage per transport session.

Methods:

event_store ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L68" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

event_store(self) -> EventStore | None

event_store ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L76" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

event_store(self, event_store: EventStore | None) -> None

StreamableHTTPASGIApp ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L80" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

ASGI application wrapper for Streamable HTTP server transport.

HostOriginGuardMiddleware ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L227" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Validate Host and Origin headers before requests reach MCP sessions.

StarletteWithLifespan ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L348" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Methods:

lifespan ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L350" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

lifespan(self) -> Lifespan[Starlette]

RequestContextMiddleware ^{<a href="https://github.com/PrefectHQ/fastmcp/blob/main/fastmcp_slim/fastmcp/server/http.py#L363" target="_blank"><Icon icon="github" style="width: 14px; height: 14px;" /></a>}

Middleware that stores each request in a ContextVar and sets transport type.