WorkOS 🤝 FastMCP

Authenticate FastMCP servers with WorkOS Connect

New in version: 2.12.0

Secure your FastMCP server with WorkOS Connect authentication. This integration uses the OAuth Proxy pattern to handle authentication through WorkOS Connect while maintaining compatibility with MCP clients.

This guide covers WorkOS Connect applications. For Dynamic Client Registration (DCR) with AuthKit, see the AuthKit integration instead.

Configuration

Prerequisites

Before you begin, you will need:

1. A WorkOS Account with access to create OAuth Apps
2. Your FastMCP server’s URL (can be localhost for development, e.g., http://localhost:8000)

Step 1: Create a WorkOS OAuth App

Create an OAuth App in your WorkOS dashboard to get the credentials needed for authentication:

1. Create OAuth Application

   In your WorkOS dashboard:

   1. Navigate to Applications
   2. Click Create Application
   3. Select OAuth Application
   4. Name your application
2. Get Credentials

   In your OAuth application settings:

   1. Copy your Client ID (starts with client_)
   2. Click Generate Client Secret and save it securely
   3. Copy your AuthKit Domain (e.g., https://your-app.authkit.app)
3. Configure Redirect URI

   In the Redirect URIs section:

   • Add: http://localhost:8000/auth/callback (for development)
   • For production, add your server’s public URL + /auth/callback

   The callback URL must match exactly. The default path is /auth/callback, but you can customize it using the redirect_path parameter.

Step 2: FastMCP Configuration

Create your FastMCP server using the WorkOSProvider:

server.py

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

# Configure WorkOS OAuth
auth = WorkOSProvider(
    client_id="client_YOUR_CLIENT_ID",
    client_secret="YOUR_CLIENT_SECRET",
    authkit_domain="https://your-app.authkit.app",
    base_url="http://localhost:8000",
    required_scopes=["openid", "profile", "email"]
)

mcp = FastMCP("WorkOS Protected Server", auth=auth)

@mcp.tool
def protected_tool(message: str) -> str:
    """This tool requires authentication."""
    return f"Authenticated user says: {message}"

if __name__ == "__main__":
    mcp.run(transport="http", port=8000)

Testing

Running the Server

Start your FastMCP server with HTTP transport to enable OAuth flows:

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

Your server is now running and protected by WorkOS OAuth authentication.

Testing with a Client

Create a test client that authenticates with your WorkOS-protected server:

client.py

from fastmcp import Client
import asyncio

async def main():    
    # The client will automatically handle WorkOS OAuth
    async with Client("http://localhost:8000/mcp", auth="oauth") as client:
        # First-time connection will open WorkOS login in your browser
        print("✓ Authenticated with WorkOS!")
        
        # Test the protected tool
        result = await client.call_tool("protected_tool", {"message": "Hello!"})
        print(result)

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

When you run the client for the first time:

1. Your browser will open to WorkOS’s authorization page
2. After you authorize the app, you’ll be redirected back
3. The client receives the token and can make authenticated requests

The client caches tokens locally, so you won’t need to re-authenticate for subsequent runs unless the token expires or you explicitly clear the cache.

Production Configuration

New in version: 2.13.0

For production deployments with persistent token management across server restarts, configure jwt_signing_key, and client_storage:

server.py

import os
from fastmcp import FastMCP
from fastmcp.server.auth.providers.workos import WorkOSProvider
from key_value.aio.stores.redis import RedisStore
from key_value.aio.wrappers.encryption import FernetEncryptionWrapper
from cryptography.fernet import Fernet

# Production setup with encrypted persistent token storage
auth = WorkOSProvider(
    client_id="client_YOUR_CLIENT_ID",
    client_secret="YOUR_CLIENT_SECRET",
    authkit_domain="https://your-app.authkit.app",
    base_url="https://your-production-domain.com",
    required_scopes=["openid", "profile", "email"],

    # Production token management
    jwt_signing_key=os.environ["JWT_SIGNING_KEY"],
    client_storage=FernetEncryptionWrapper(
        key_value=RedisStore(
            host=os.environ["REDIS_HOST"],
            port=int(os.environ["REDIS_PORT"])
        ),
        fernet=Fernet(os.environ["STORAGE_ENCRYPTION_KEY"])
    )
)

mcp = FastMCP(name="Production WorkOS App", auth=auth)

Parameters (jwt_signing_key and client_storage) work together to ensure tokens and client registrations survive server restarts. Wrap your storage in FernetEncryptionWrapper to encrypt sensitive OAuth tokens at rest - without it, tokens are stored in plaintext. Store secrets in environment variables and use a persistent storage backend like Redis for distributed deployments.

For complete details on these parameters, see the OAuth Proxy documentation.

Environment Variables

New in version: 2.12.1

For production deployments, use environment variables instead of hardcoding credentials.

Provider Selection

Setting this environment variable allows the WorkOS provider to be used automatically without explicitly instantiating it in code.

FASTMCP_SERVER_AUTH · default: "Not set"

Set to fastmcp.server.auth.providers.workos.WorkOSProvider to use WorkOS authentication.

WorkOS-Specific Configuration

These environment variables provide default values for the WorkOS provider, whether it’s instantiated manually or configured via FASTMCP_SERVER_AUTH.

FASTMCP_SERVER_AUTH_WORKOS_CLIENT_ID · required

Your WorkOS OAuth App Client ID (e.g., client_01K33Y6GGS7T3AWMPJWKW42Y3Q)

FASTMCP_SERVER_AUTH_WORKOS_CLIENT_SECRET · required

Your WorkOS OAuth App Client Secret

FASTMCP_SERVER_AUTH_WORKOS_AUTHKIT_DOMAIN · required

Your WorkOS AuthKit domain (e.g., https://your-app.authkit.app)

FASTMCP_SERVER_AUTH_WORKOS_BASE_URL · default: "http://localhost:8000"

Public URL where OAuth endpoints will be accessible (includes any mount path)

FASTMCP_SERVER_AUTH_WORKOS_ISSUER_URL · default: "Uses BASE_URL"

Issuer URL for OAuth metadata (defaults to BASE_URL). Set to root-level URL when mounting under a path prefix to avoid 404 logs. See HTTP Deployment guide for details.

FASTMCP_SERVER_AUTH_WORKOS_REDIRECT_PATH · default: "/auth/callback"

Redirect path configured in your WorkOS OAuth App

FASTMCP_SERVER_AUTH_WORKOS_REQUIRED_SCOPES · default: "[]"

Comma-, space-, or JSON-separated list of required OAuth scopes (e.g., openid profile email or ["openid","profile","email"])

FASTMCP_SERVER_AUTH_WORKOS_TIMEOUT_SECONDS · default: "10"

HTTP request timeout for WorkOS API calls

Example .env file:

# WorkOS OAuth credentials (always used as defaults)
FASTMCP_SERVER_AUTH_WORKOS_CLIENT_ID=client_01K33Y6GGS7T3AWMPJWKW42Y3Q
FASTMCP_SERVER_AUTH_WORKOS_CLIENT_SECRET=your_client_secret
FASTMCP_SERVER_AUTH_WORKOS_AUTHKIT_DOMAIN=https://your-app.authkit.app
FASTMCP_SERVER_AUTH_WORKOS_BASE_URL=https://your-server.com
FASTMCP_SERVER_AUTH_WORKOS_REQUIRED_SCOPES=["openid","profile","email"]

# Optional: Automatically provision WorkOS auth for all servers
FASTMCP_SERVER_AUTH=fastmcp.server.auth.providers.workos.WorkOSProvider

With environment variables set, you can either:

Option 1: Manual instantiation (env vars provide defaults)

server.py

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

# Env vars provide default values for WorkOSProvider()
auth = WorkOSProvider()  # Uses env var defaults
mcp = FastMCP(name="WorkOS Protected Server", auth=auth)

Option 2: Automatic provisioning (requires FASTMCP_SERVER_AUTH=fastmcp.server.auth.providers.workos.WorkOSProvider)

server.py

from fastmcp import FastMCP

# Auth is automatically provisioned from FASTMCP_SERVER_AUTH
mcp = FastMCP(name="WorkOS Protected Server")

Configuration Options

client_id · required

WorkOS OAuth application client ID

client_secret · required

WorkOS OAuth application client secret

authkit_domain · required

Your WorkOS AuthKit domain URL (e.g., https://your-app.authkit.app)

base_url · required

Your FastMCP server’s public URL

required_scopes · default: "[]"

OAuth scopes to request

redirect_path · default: "/auth/callback"

OAuth callback path

timeout_seconds · default: "10"

API request timeout