If my memory serves me right it was not much more earlier JSON became first class citizen in web browsers. As I remember it, the biggest pain with using JSON at the time for me was; serializing and de-serializing JSON to and from string. Also Newton King released what has now become a de-facto library (more or less) for working with JSON in .Net.
Five years ago, I was not thinking of REST the same way I do today. Today REST is integral part of any integration I create, at least on the provider side. When getting back a response back from REST API, I like to get the status property of the request directly inside the json object. Another advantage of getting status in response body is; you can look for status property while checking the health of your service with i.e. Application Insights. Plus I have learned not to rely just on HTTP status codes, as some developers just use 200 Ok for everything.
To keep myself using an standard I googled, if someone else has come up with something in line with my initial idea. I found JSend.