Agent MCP Directory

Remote MCP auth patterns compared

Pick between an open server, an API key and OAuth with or without client registration, and see what each looks like to an agent and in this directory. Of 817 reachable endpoints, 263 need no credentials and 533 publish OAuth metadata.

Steps

  1. Decide who the server is for: a public docs server can stay open, a product server acts for a signed-in user.
  2. Open: list tools to any client and keep anything sensitive out of reach.
  3. API key: answer 401 with a message a person can act on; an agent cannot register itself for a key.
  4. OAuth: publish protected resource metadata so a client finds the flow without a person wiring it.
  5. Test the 401 challenge, the metadata documents and PKCE with S256 before launch.

What the sources say

  • Ora's catalog grades auth by fit: docs MCP servers should be public and product MCP servers should require OAuth. (ora.ai, read 5 November 2026)
  • Ora checks OAuth metadata under RFC 8414 as a way for agents to discover the sign-in flow automatically. (ora.ai, read 5 November 2026)
  • Ora checks that the OAuth flow supports PKCE with the S256 method. (ora.ai, read 5 November 2026)
  • The 2026-07-28 MCP specification requires servers to implement OAuth 2.0 Protected Resource Metadata (RFC 9728). (modelcontextprotocol.io, read 4 November 2026)
  • Clients obtain a client ID through Client ID Metadata Documents, pre-registration or Dynamic Client Registration; the specification marks CIMD as SHOULD and DCR as MAY and deprecated. (modelcontextprotocol.io, read 4 November 2026)
  • Ora says that when an MCP server requires authentication, a scan returns MCP_AUTH_REQUIRED with no score or grade. (ora.ai, read 5 November 2026)

The four patterns in the directory

Reachable MCP endpoints by auth typeNo authentication: 263; API key: 19; OAuth with client registration: 517; OAuth without client registration: 16No authentication263API key19OAuth with client registration517OAuth without client registration16Reachable endpoints
Reachable endpoints by the auth type the connector saw on 4 November 2026. The table has the same counts, what a client sees and four of the most visited examples.
Auth patterns, what a client sees and who uses each
PatternEndpointsTools listedWhat a client seesExamples
No authentication263263The server listed its tools to a client that sent no credentials.Google, Cloudflare, Google Cloud, Microsoft
API key190The server answered 401 or 403 and asks for a key or bearer token with no OAuth metadata for an agent to follow.StackOverflow, Appcircle, Bitculator, Cavyro
OAuth with client registration5170The server publishes OAuth metadata and a registration endpoint, so a client can register itself without a human filling in a form first.Sentry, PayPal, Stripe, Amplitude
OAuth without client registration160The server publishes OAuth metadata but no registration endpoint, so a client must be registered by hand or identified by a client ID metadata document.GitHub, Microsoft 365, Zoom, HubSpot

What a scanner expects

Ora's catalog grades the match between a server's auth and its job: docs servers should be public and product servers should require OAuth, and its check asks whether the auth matches what the server does. A server that requires sign-in cannot be scored from outside at all; Ora returns MCP_AUTH_REQUIRED with no score or grade. How Ora tests an MCP server and the OAuth checks.

The OAuth route itself, with client ID metadata documents and dynamic registration, is in the OAuth guide.