diff --git a/docs/DEVELOPER-GUIDE.md b/docs/DEVELOPER-GUIDE.md
index f412238..364d1dd 100644
--- a/docs/DEVELOPER-GUIDE.md
+++ b/docs/DEVELOPER-GUIDE.md
@@ -778,9 +778,10 @@ Internet → Traefik → Service:8080 → Auth Sidecar:8080 → localhost → Yo
 
 ### Authentication Modes
 
-Two authentication modes are supported:
+Three authentication modes are supported:
 1. **Token-based**: Static tokens (simple, good for service-to-service or internal apps)
 2. **OIDC**: OpenID Connect (full SSO, good for user-facing apps)
+3. **MCP**: OAuth 2.0 for MCP servers via RFC 9728 / RFC 7591 (good for MCP tool servers requiring OAuth-based access control)
 
 ---