MCP (Model Context Protocol) has an auth story on paper: OAuth 2.1 with PKCE, dynamic client registration, resource indicators per RFC 8707. In practice I kept running into servers that were missing most of it. So I spent a week building patchbay audit , a free CLI that pokes an MCP server and reports what it finds. Then I pointed it at 25 public endpoints.

The numbers

25 servers scanned on 2026-11-02. All publicly listed in community directories or vendor docs. URL list in the repo .

Count

Reachable 20/25

Enforce authentication 12/25

Reachable + public (no auth) 8/20

Of those public: expose a mutating tool 2/8

Advertise OAuth 2.1 discovery metadata 2/20

Advertise resource_indicators_supported (RFC 8707) 2/20

Advertise PKCE S256 in code_challenge_methods_supported 2/20

Three servers initially triggered critical findings.…