New in version: 2.12.4 This guide shows you how to secure your FastMCP server using Auth0 OAuth. While Auth0 does have support for Dynamic Client Registration, it is not enabled by default so this integration uses the OIDC Proxy pattern to bridge Auth0’s dynamic OIDC configuration with MCP’s authentication requirements.

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Configuration

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Prerequisites

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

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Step 1: Create an Auth0 Application

Create an Application in your Auth0 settings to get the credentials needed for authentication:
1

Navigate to Applications

Go to Applications → Applications in your Auth0 account.Click ”+ Create Application” to create a new application.
2

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
3

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.
4

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.
5

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.

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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")
    }

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Testing

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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.

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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")
        print(f"Auth0 audience: {result['audience']}")

if __name__ == "__main__":
    asyncio.run(main())
When you run the client for the first time:
  1. Your browser will open to Auth0’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.

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Environment Variables

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

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Provider Selection

Setting this environment variable allows the Auth0 provider to be used automatically without explicitly instantiating it in code.

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FASTMCP_SERVER_AUTH
default:"Not set"
Set to fastmcp.server.auth.providers.auth0.Auth0Provider to use Auth0 authentication.

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Auth0-Specific Configuration

These environment variables provide default values for the Auth0 provider, whether it’s instantiated manually or configured via FASTMCP_SERVER_AUTH.

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FASTMCP_SERVER_AUTH_AUTH0_CONFIG_URL
required
Your Auth0 Application Configuration URL (e.g., https://.../.well-known/openid-configuration)
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FASTMCP_SERVER_AUTH_AUTH0_CLIENT_ID
required
Your Auth0 Application Client ID (e.g., tv2ObNgaZAWWhhycr7Bz1LU2mxlnsmsB)
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FASTMCP_SERVER_AUTH_AUTH0_CLIENT_SECRET
required
Your Auth0 Application Client Secret (e.g., vPYqbjemq...)
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FASTMCP_SERVER_AUTH_AUTH0_AUDIENCE
required
Your Auth0 API Audience
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FASTMCP_SERVER_AUTH_AUTH0_BASE_URL
required
Public URL of your FastMCP server for OAuth callbacks
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FASTMCP_SERVER_AUTH_AUTH0_REDIRECT_PATH
default:"/auth/callback"
Redirect path configured in your Auth0 Application
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FASTMCP_SERVER_AUTH_AUTH0_REQUIRED_SCOPES
default:"[\"openid\"]"
Comma-, space-, or JSON-separated list of required AUth0 scopes (e.g., openid email or ["openid","email"])
Example .env file: 
# Use the Auth0 provider
FASTMCP_SERVER_AUTH=fastmcp.server.auth.providers.auth0.Auth0Provider

# Auth0 configuration and credentials
FASTMCP_SERVER_AUTH_AUTH0_CONFIG_URL=https://.../.well-known/openid-configuration
FASTMCP_SERVER_AUTH_AUTH0_CLIENT_ID=tv2ObNgaZAWWhhycr7Bz1LU2mxlnsmsB
FASTMCP_SERVER_AUTH_AUTH0_CLIENT_SECRET=vPYqbjemq...
FASTMCP_SERVER_AUTH_AUTH0_AUDIENCE=https://...
FASTMCP_SERVER_AUTH_AUTH0_BASE_URL=https://your-server.com
FASTMCP_SERVER_AUTH_AUTH0_REQUIRED_SCOPES=openid,email
With environment variables set, your server code simplifies to:
server.py
from fastmcp import FastMCP

# Authentication is automatically configured from environment
mcp = FastMCP(name="Auth0 Secured App")

@mcp.tool
async def search_logs() -> list[str]:
    """Search the service logs."""
    # Your tool implementation here
    pass