REST is designed to be visible and simple. Visibility of the service means that every aspect of it should self-descriptive and follow the natural HTTP language according to principles 3, 4, and 5.
Visibility in the context of the outer world would mean that monitoring applications would be interested only in the HTTP communication between the REST service and the caller. Since the requests and responses are stateless and atomic, nothing more is needed to flow the behavior of the application and to understand whether anything has gone wrong.
Remember that caching reduces the visibility of your RESTful applications and in general should be avoided, unless needed for serving resources subject to large amounts of callers. In such cases, caching may be an option, after carefully evaluating the possible consequences of serving obsolete data.