It seems like on Codeforces API, everybody has zero contribution, even if in reality, they have positive contribution. For instance, if you take a look at the list of rated users, jiangly appears to have contribution 0, when in reality his contribution is over 100. The same goes for other users like tourist, um_nik, and so forth.
I think this should be an easy thing to fix. Would appreciate if it gets fixed :).