You're assuming you only have to define it in one language. JSON is an interchange format. The canonical way to express it is JSON Schema, and the tools are unp

You're assuming you only have to define it in one language. JSON is an interchange format. The canonical way to express it is JSON Schema, and the tools are unpleasant in Java. So is dealing with structural typing of polymorphic responses. In an ideal world we wouldn't have those, but we live in this one. These things are just better when you aren't in a nominatively typed language with some pretty crusty assumptions.