All of these concerns and recommendations are exactly what make my stomach curl when I think of webservices, e.g.,
Design the interface as a dictionary, though not as an object based wrapper around dictionaries (ie prefer a Map over a Bean). I’ve seen Python and Lisp code that does this well as they have good support for meta-class hacking; and it’s sometimes called data-driven programming in the Lisp world.
Ahhhh! To me — a type-safety, contract-based coding, OO nut — webservices are a massive step backwards into the procedural flaming swamp-world I despise.