I have seen too many front end developers write queries equivalent to "select * from users, t1, t2, ... tn, left outer join on users.id = t1.user_id... etc etc etc".
I think that is just bullshit.
I prefer to tell the frontend people - these are the endpoints that backend team provides, go live with it. If you really have issues, talk to them, and they might just add a new endpoint for you.
If you let frontend developers dictate backend queries, all you will get is a big master cluster fuck. I am talking average joe developers that we usually find to work on startups.