A standard for building APIs in JSON
I would say there is no need for this.JSON/REST are beloved because it's simple and just works. Originally XML itself was simple too with just DTD as "Schema".BUT then all the additional standards like XMLSchema, XSLT, XML-RPC/SOAP turned it in an ugly duck.  JSON API is extracted from the JSON transport implicitly 
  defined by Ember Data's REST adapter. 
  http://jsonapi.org/about/

As JSON-API comes from the Ember.js camp, I remember the Ember vs. Angular discussions on HN 1-2 years ago. Google Trends shows Ember.js has gone nowhere. https://www.google.com/trends/explore#q=AngularJS%2C%20Ember... (and now there is also React). So I guess the "Ember.js way" to do things failed. At some point we should learn from history, and not turn JSON into SOAP/WSDL - https://xkcd.com/927/ .XML-RPC/SOAP and/or many other remote procedure call transport techniques failed in in the long term and are a big pile of legacy mess (CORBA, DCOM, RMI, SAP RFC, .NET Remoting, XML-RPC, etc.):  http://en.wikipedia.org/wiki/Remote_procedure_call