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.

Django REST Django is a Python-based REST framework used frequently by developers to build extremely fast and reliable APIs.

SIHOT, one of the leading hotel management systems, has upgraded its SIHOT@360º API by incorporating new REST (Representational State Transfer) ...