AuthKit 🤝 FastMCP

Secure your FastMCP server with AuthKit by WorkOS

This guide shows you how to secure your FastMCP server using WorkOS’s AuthKit, a complete authentication and user management solution. This integration uses the Remote OAuth pattern, where AuthKit handles user login and your FastMCP server validates the tokens.

Configuration

Prerequisites

Before you begin, you will need:

1. A WorkOS Account and a new Project.
2. An AuthKit instance configured within your WorkOS project.
3. Your FastMCP server’s URL (can be localhost for development, e.g., http://localhost:8000).

Step 1: AuthKit Configuration

In your WorkOS Dashboard, enable AuthKit and configure the following settings:

1. Enable Dynamic Client Registration

   Go to Applications → Configuration and enable Dynamic Client Registration. This allows MCP clients register with your application automatically.

   
2. Note Your AuthKit Domain

   Find your AuthKit Domain on the configuration page. It will look like https://your-project-12345.authkit.app. You’ll need this for your FastMCP server configuration.

Step 2: FastMCP Configuration

Create your FastMCP server file and use the AuthKitProvider to handle all the OAuth integration automatically:

server.py

from fastmcp import FastMCP
from fastmcp.server.auth.providers.workos import AuthKitProvider

# The AuthKitProvider automatically discovers WorkOS endpoints
# and configures JWT token validation
auth_provider = AuthKitProvider(
    authkit_domain="https://your-project-12345.authkit.app",
    base_url="http://localhost:8000"  # Use your actual server URL
)

mcp = FastMCP(name="AuthKit Secured App", auth=auth_provider)

Testing

To test your server, you can use the fastmcp CLI to run it locally. Assuming you’ve saved the above code to server.py (after replacing the authkit_domain and base_url with your actual values!), you can run the following command:

fastmcp run server.py --transport http --port 8000

Now, you can use a FastMCP client to test that you can reach your server after authenticating:

from fastmcp import Client
import asyncio

async def main():
    async with Client("http://localhost:8000/mcp", auth="oauth") as client:
        assert await client.ping()

if __name__ == "__main__":
    asyncio.run(main())

Production Configuration

For production deployments, load sensitive configuration from environment variables:

server.py

import os
from fastmcp import FastMCP
from fastmcp.server.auth.providers.workos import AuthKitProvider

# Load configuration from environment variables
auth = AuthKitProvider(
    authkit_domain=os.environ.get("AUTHKIT_DOMAIN"),
    base_url=os.environ.get("BASE_URL", "https://your-server.com")
)

mcp = FastMCP(name="AuthKit Secured App", auth=auth)