Proper HTTP status codes improve REST API clarity. 2xx codes indicate success (e.g., 200 OK, 201 Created), 4xx codes signal client errors (e.g., 400 Bad Request, 404 Not Found), and 5xx codes represent server issues (e.g., 500 Internal Server Error). Clear error messages and response structures, like using JSON { "error": "Invalid request" }, help clients handle issues efficiently. Implementing meaningful status codes and error handling improves API usability and debugging.