Auth0 Auth for MCP Example

Protects a FastMCP server with Auth0 Auth for MCP. Auth0 handles OAuth and client registration; FastMCP validates access tokens.

Auth0 setup

1. Enable Resource Parameter Compatibility Profile (Settings → Advanced).
2. Create an API whose identifier is http://127.0.0.1:8000/mcp (must match the URL logged at server startup).
3. Promote your login connections to domain-level (required for third-party DCR clients).

See Auth0's authorization quickstart for details.

Running

export AUTH0_CONFIG_URL="https://YOUR_TENANT.auth0.com/.well-known/openid-configuration"
python server.py

In another terminal:

python client.py

Use 127.0.0.1 consistently — mixing localhost and 127.0.0.1 breaks audience validation.

For troubleshooting (DCR grants, token exchange errors, MCP Inspector), see the Auth0 integration guide.