I'm definitely in the lenient camp on a [simple -- complex] scale. So, I agree JSON/REST are simple and just works, for most tasks. That's certainly how I've us

I'm definitely in the lenient camp on a [simple -- complex] scale. So, I agree JSON/REST are simple and just works, for most tasks. That's certainly how I've used the two technologies mostly. But I definitely see some benefits with json-api. Here are two: 1. When writing large single-page apps in JS, client <-> backend communication will need some structure. Could be a few project-internal guidelines, or something like json-api. 2. Client frameworks and backend frameworks are often separate projects (e.g. Django/express/sinatra server-side or React/Backbone/Mithril client-side). It's helpful with a standard to converge on for authors of backend json/rest serializers, and data adapters client-side. I'm not expert of RPC's, but I'm pretty sure it's something quite different from jsonapi.