The API should use qualified IDs (e.g. "Q1234") everywhere - when giving IDs as parameters, in input JSON, in output data. This would improve consistency, avoid confusion, and would allow seamless operations on different types of entities without caring about the type at hand.
I believe it would even be good to use qualified IDs internally too, in the PHP classes, maybe even in the database.
Whiteboard: storypoints: 13