Auth0 OAuth 🤝 FastMCP

FastMCP supports two Auth0 integration paths:

Auth for MCP — Auth0 handles OAuth, DCR, and CIMD; FastMCP validates tokens (Auth0MCPProvider). Use this for MCP-native clients and Auth0’s Auth for MCP setup.
OIDC Proxy — FastMCP proxies OAuth with fixed application credentials (Auth0Provider). Use this when you manage an Auth0 application manually and do not need tenant-level DCR.

Auth for MCP (DCR)

This path uses the Remote OAuth pattern. Auth0 acts as the authorization server; FastMCP is the resource server.

Prerequisites

An Auth0 account with Auth for MCP enabled
Resource Parameter Compatibility Profile enabled (Settings → Advanced)
Your FastMCP server URL (use http://127.0.0.1:8000 in development — not localhost)

See Auth0’s authorization quickstart for tenant setup (API identifier, domain-level connections, CIMD approval).

Step 1: Create an Auth0 API

Create an API (Resource Server) whose identifier is your MCP resource URL, for example http://127.0.0.1:8000/mcp. Use RS256 signing and the rfc9068_profile_authz token dialect if you need permissions claims on tokens. When the server starts, it logs the exact aud value it validates — your API identifier must match.

Step 2: FastMCP configuration

server_mcp.py

from fastmcp import FastMCP
from fastmcp.server.auth.providers.auth0 import Auth0MCPProvider

auth_provider = Auth0MCPProvider(
    config_url="https://YOUR_TENANT.auth0.com/.well-known/openid-configuration",
    base_url="http://127.0.0.1:8000",
)

mcp = FastMCP(name="Auth0 MCP Server", auth=auth_provider)

No client_id or client_secret is required on the FastMCP side — MCP clients register with Auth0 directly.

Testing

See examples/auth/auth0_mcp/ for a runnable server and DCR client. Set AUTH0_CONFIG_URL to your tenant’s OIDC discovery URL before starting the server.

OIDC Proxy (fixed credentials)

This integration uses the OIDC Proxy pattern when you use a fixed Auth0 application instead of tenant-level DCR.

Prerequisites

Before you begin, you will need:

An Auth0 Account with access to create Applications
Your FastMCP server’s URL (can be localhost for development, e.g., http://localhost:8000)

Step 1: Create an Auth0 Application

Create an Application in your Auth0 settings to get the credentials needed for authentication:

Navigate to Applications

Go to Applications → Applications in your Auth0 account.Click ”+ Create Application” to create a new application.

Create Your Application

Name: Choose a name users will recognize (e.g., “My FastMCP Server”)
Choose an application type: Choose “Single Page Web Applications”
Click Create to create the application

Configure Your Application

Select the “Settings” tab for your application, then find the “Application URIs” section.

Allowed Callback URLs: Your server URL + /auth/callback (e.g., http://localhost:8000/auth/callback)
Click Save to save your changes

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

If you want to use a custom callback path (e.g., /auth/auth0/callback), make sure to set the same path in both your Auth0 Application settings and the redirect_path parameter when configuring the Auth0Provider.

Save Your Credentials

After creating the app, in the “Basic Information” section you’ll see:

Client ID: A public identifier like tv2ObNgaZAWWhhycr7Bz1LU2mxlnsmsB
Client Secret: A private hidden value that should always be stored securely

Store these credentials securely. Never commit them to version control. Use environment variables or a secrets manager in production.

Select Your Audience

Go to Applications → APIs in your Auth0 account.

Find the API that you want to use for your application
API Audience: A URL that uniquely identifies the API

Store this along with of the credentials above. Never commit this to version control. Use environment variables or a secrets manager in production.

Step 2: FastMCP Configuration

Create your FastMCP server using the Auth0Provider.

server.py

from fastmcp import FastMCP
from fastmcp.server.auth.providers.auth0 import Auth0Provider

# The Auth0Provider utilizes Auth0 OIDC configuration
auth_provider = Auth0Provider(
    config_url="https://.../.well-known/openid-configuration",  # Your Auth0 configuration URL
    client_id="tv2ObNgaZAWWhhycr7Bz1LU2mxlnsmsB",               # Your Auth0 application Client ID
    client_secret="vPYqbjemq...",                               # Your Auth0 application Client Secret
    audience="https://...",                                     # Your Auth0 API audience
    base_url="http://localhost:8000",                           # Must match your application configuration
    # redirect_path="/auth/callback"                            # Default value, customize if needed
)

mcp = FastMCP(name="Auth0 Secured App", auth=auth_provider)

# Add a protected tool to test authentication
@mcp.tool
async def get_token_info() -> dict:
    """Returns information about the Auth0 token."""
    from fastmcp.server.dependencies import get_access_token

    token = get_access_token()

    return {
        "issuer": token.claims.get("iss"),
        "audience": token.claims.get("aud"),
        "scope": token.claims.get("scope")
    }

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 Auth0 authentication.

Testing with a Client

Create a test client that authenticates with your Auth0-protected server:

test_client.py

from fastmcp import Client
import asyncio

async def main():
    # The client will automatically handle Auth0 OAuth flows
    async with Client("http://localhost:8000/mcp", auth="oauth") as client:
        # First-time connection will open Auth0 login in your browser
        print("✓ Authenticated with Auth0!")

        # Test the protected tool
        result = await client.call_tool("get_token_info")
        token_info = result.data
        print(f"Auth0 audience: {token_info['audience']}")

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

When you run the client for the first time:

Your browser will open to Auth0’s authorization page
After you authorize the app, you’ll be redirected back
The client receives the token and can make authenticated requests

Production Configuration

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.auth0 import Auth0Provider
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_provider = Auth0Provider(
    config_url="https://.../.well-known/openid-configuration",
    client_id="tv2ObNgaZAWWhhycr7Bz1LU2mxlnsmsB",
    client_secret="vPYqbjemq...",
    audience="https://...",
    base_url="https://your-production-domain.com",

    # 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 Auth0 App", auth=auth_provider)

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.

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.

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Auth0 OAuth 🤝 FastMCP

Auth for MCP (DCR)

Prerequisites

Step 1: Create an Auth0 API

Step 2: FastMCP configuration

Testing

OIDC Proxy (fixed credentials)

Prerequisites

Step 1: Create an Auth0 Application

Step 2: FastMCP Configuration

Testing

Running the Server

Testing with a Client

Production Configuration

​Auth for MCP (DCR)

​Prerequisites

​Step 1: Create an Auth0 API

​Step 2: FastMCP configuration

​Testing

​OIDC Proxy (fixed credentials)

​Prerequisites

​Step 1: Create an Auth0 Application

​Step 2: FastMCP Configuration

​Testing

​Running the Server

​Testing with a Client

​Production Configuration

Auth for MCP (DCR)

Prerequisites

Step 1: Create an Auth0 API

Step 2: FastMCP configuration

Testing

OIDC Proxy (fixed credentials)

Prerequisites

Step 1: Create an Auth0 Application

Step 2: FastMCP Configuration

Testing

Running the Server

Testing with a Client

Production Configuration