[marcosdumay]

> because they are intended to be consumed by apps, but are not app-specific

Well, good luck designing any standard app-independent protocol that works and doesn't do that.

And yes, you must handle two nested levels of branching. That's how it works.

The only improvement possible to make it clearer is having codes for API specific errors... what 400 and 500 aren't exactly. But then, that doesn't gain you much.