RBAC and Doc updates

api/README.md

@@ -2,6 +2,15 @@
 
 REST API for managing mailing lists and members with token-based authentication.
 
+## Overview
+
+This FastAPI-based REST API provides programmatic access to the mailing list system. It's designed for:
+- **Automation**: Scripts and integrations that need to manage lists/members
+- **Web Interface**: Powers the frontend at http://localhost:3000
+- **Third-party Apps**: Any application that needs mailing list management
+
+**For most users**, the web interface (http://localhost:3000) is more convenient. Use this API when you need programmatic access or automation.
+
 ## Base URL
 
 ```