In NSX-T version 2.4 VMware introduced a new API to configure and manage virtual network environment. VMware refers to the new API as the Policy API. The Policy API does not replace the more traditional API available in the previous versions of NSX-T. We refer to the old API as the management plane API. Any existing script or automation programmed against the management plane API will still work, but now a new and more modern approach to automate the NSX network is also available.
Luca Carmada wrote an introduction note to Policy API here.
These JSON file is the template file, you can run it in Postman by importing the collection JSON file.