If we need to follow that logic (to include useful non-primitives) we would end up with a clusterfuck of a spec that noone would want to implement.

This hypothetical generic client always comes up in discussions of data formats and RESTful APIs. But I've never understood what use it could be. It seems to me that any meaningful software (i.e., anything beyond a debugging tool) that would consume data or an API would need a more specific UI than a tree view with links.