API-Key: <API key> header. Here are examples for the most common clients.
Clients not listed here also connect with the same URL and
API-Key header as long as they support Streamable HTTP. For clients that only support stdio, bridge with npx mcp-remote <URL> --header "API-Key: …".The web connectors in Claude.ai and ChatGPT use OAuth authentication instead of entering an API key directly. See Web connectors for how to connect and OAuth 2.1 for the technical flow.