Version 4.4 contains the "scaffolding" as Matthew Mullenweg, founding developer of WordPress put it in his own intro. To be sure, WordPress is not the first CMS to incorporate the REST API framework.

Flask Restful is a Python-based micro-framework used by developers to make micro web services. It has a very lightweight module which makes it easy to build and implement APIs quickly.

Software developers are demanding APIs that are delivered in a RESTful, resource based way, and one way to do that is by building with the RESTlet framework.