> You are allowed to deconstruct the id that way because it's the only way to get the information.

If the API has a usable purpose without providing that info, then I think I'd disagree with you - since you're reverse-engineering the implementation to get more data out.

Reverse engineering is OK, but implicitly carries the risk that stuff will change and break you without warning, in which case you can't really complain, in my opinion.

If the API's purpose can't be fulfilled without that info, then the API was probably broken as designed (you needed to parse the id to get the info, they just didn't document it).