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Notes on mounting remote MCP, Streamable HTTP, and serverless ASGI.

  • in mcp, asgi
  • 1 min read

Why mcp-asgi-http exists

The official MCP Python SDK and FastMCP can expose Streamable HTTP. Tutorials show app.mount("/mcp", ...). That is enough for local demos.

Problems show up when you put the same pattern on Mangum with lifespan="off", share auth with a REST API, or hit Function URL slash redirects. This package is the small set of helpers we kept rewriting for that case:

  1. Stateless Streamable HTTP ASGI app (JSON responses, no session store)
  2. Path middleware instead of Mount for /mcp
  3. Optional API key / JWT / dual auth, or auth=None if the gateway already authenticated
  4. once_ready for lazy init when lifespan never runs

It is not a tool framework. Register tools with the official SDK (or FastMCP). Use this to mount and protect /mcp next to your existing API.