Excuse my ignorance, but isn't this essentially a tight(er) coupling between the client and the server, something we have been trying to avoid with REST and, especially, HATEOAS? What happened to API “discoverability”? As I understood HATEOAS, the point was that the client just had to know how to work with particular data types (that's the point of an API, really), but was not expected to know or construct URLs beforehand, thus loosening the coupling to the server. Did I get it wrong? Did that path prove to be unrealistic?