As I understand it, there's a lot of places overhead creeps in that tends to make this sort of thing vastly more efficient than making multiple calls. Sure you'll maybe send data people don't want this time, but it will probably save processing and networking overhead that would be spent building and sending a long list of the fields they want. When designing an API I tend to lean to being a bit more verbose than I need to be, if only to save the HTTP overhead of another request. At least until HTTP2 helps us out there.