closedmcp

A small Python wrapper for Log in with ClosedMCP. It protects Streamable HTTP requests made to the official SDK’s Server or built-in FastMCP, or standalone FastMCP 2, verifies a signed pass on every call, and serves MCP protected-resource metadata.

Add to an existing server

Keep your existing official mcp.server.fastmcp.FastMCP or standalone fastmcp.FastMCP 2 instance. Replace its HTTP serving call with:

import os
from closedmcp import current_user, serve_with_closedmcp
serve_with_closedmcp(app, resource=os.environ["MCP_URL"], allowed_domains=os.environ["ALLOWED_DOMAINS"].split(","))

In any tool, use current_user().email or current_user().org. For an existing ASGI host, serve closedmcp_app(app, resource=..., allowed_domains=...) instead. Install with pip install closedmcp for the official SDK or pip install 'closedmcp[fastmcp]' for standalone FastMCP 2.

Hello

from mcp.server.fastmcp import FastMCP
from closedmcp import current_user, serve_with_closedmcp
app = FastMCP("hello")
@app.tool()
def hello() -> str:
    return f"Hello {current_user().email}"
serve_with_closedmcp(
    app,
    resource="https://example.com/mcp",
    allowed_domains=["example.com"])

Replace the first import with from fastmcp import FastMCP to use standalone FastMCP 2. Install with pip install closedmcp for the official SDK or pip install 'closedmcp[fastmcp]' for both. This repository also has a runnable template: install the package locally with pip install -e ., then run MCP_URL=https://example.com/mcp ALLOWED_DOMAINS=example.com python template/server.py. Set PORT and HOST for the listening socket. CLOSEDMCP_ORIGIN and CLOSEDMCP_JWKS_URL are available for local integration tests.

resource is the exact public MCP URL and JWT audience. allowed_domains must contain at least one verified company domain. The wrapper checks an EdDSA pass against the issuer's JWKS, issuer, exact audience, expiry, five-minute maximum lifetime, required identity claims, and company domain. Unknown key IDs trigger a JWKS refresh through PyJWT. current_user() returns a Person with id, email, company, org, and optional aiApp; it raises outside a verified request. aiApp is a client supplied display value.

For /mcp, metadata is at /.well-known/oauth-protected-resource/mcp and the generic metadata path. A missing or invalid pass receives 401 with WWW-Authenticate: Bearer resource_metadata="<metadata URL>". Authenticated non-POST requests receive 405. To use another ASGI server, call closedmcp_app(app, resource=..., allowed_domains=...) and serve the returned ASGI app. Its lifespan must be run by the ASGI server.

See the ClosedMCP documentation.