I don't reach for it often but I've been around the block a bit, CC processors in the iPad point of sale I built circa 2010 used it and it seemed a bit off/unnecessary.

In retrospect, its useful for creating islands of sanity/enforcement in a codebase. Lightweight way to give type annotations across organizational boundaries.

> we use an XML parser to parse it to JSON and even then it's not perfect

I can't quite picture this: how does one parse XML to JSON? I assume there's code that's parsing XML and returning a JSON object? What would make this not perfect, other than a poor implementation of the translator? Would them using JSON help? If JSON is a less expressive format than JSON, is it possible to 100% translate their XML to JSON?

> useful for creating islands of sanity/enforcement in a codebase

Thanks for the insight! Is this what JSDoc/Swagger is now used for?

> I can't quite picture this: how does one parse XML to JSON?

I'm not sure actually. I haven't personally seen the code, I just hear my coworkers always lambasting that API provider for their usage of XML. Maybe it's just their lack of documentation that sucks, but it's become a running joke whenever we get a new partner that the team integrating it jokes that their API is XML.