MCP authentication

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MCP authentication enables OAuth 2.0 protection for MCP servers, helping to implement the MCP Authorization specification. Agentgateway can act as a resource server, validating JWT tokens and exposing protected resource metadata.

There are three deployment scenarios.

Authorization Server Proxy

Agentgateway can adapt traffic for authorization servers that don’t fully comply with OAuth standards. For example, Keycloak exposes certificates at a non-standard endpoint.

In this mode, agentgateway:

• Exposes protected resource metadata on behalf of the MCP server
• Proxies authorization server metadata and client registration
• Validates tokens using the authorization server’s JWKS
• Returns 401 Unauthorized with appropriate WWW-Authenticate headers for unauthenticated requests

mcpAuthentication:
  issuer: http://localhost:7080/realms/mcp
  jwks:
    url: http://localhost:7080/protocol/openid-connect/certs
  provider:
    keycloak: {}
  resourceMetadata:
    resource: http://localhost:3000/mcp
    scopesSupported:
    - read:all
    bearerMethodsSupported:
    - header
    - body
    - query
    resourceDocumentation: http://localhost:3000/stdio/docs
    resourcePolicyUri: http://localhost:3000/stdio/policies

Resource Server Only

Agentgateway acts solely as a resource server, validating tokens issued by an external authorization server.

mcpAuthentication:
  issuer: http://localhost:9000
  jwks:
    url: http://localhost:9000/.well-known/jwks.json
  resourceMetadata:
    resource: http://localhost:3000/mcp
    scopesSupported:
    - read:all
    bearerMethodsSupported:
    - header
    - body
    - query

Authentication mode

You can control how agentgateway handles requests that lack valid credentials by setting the mode field. The following modes are supported:

The following example sets the mode to permissive:

mcpAuthentication:
  mode: permissive
  issuer: http://localhost:9000
  jwks:
    url: http://localhost:9000/.well-known/jwks.json
  resourceMetadata:
    resource: http://localhost:3000/mcp
    scopesSupported:
    - read:all

Passthrough

When the MCP server already implements OAuth authentication, no additional configuration is needed. Agentgateway will pass requests through without modification.