Google Play Games services has events mechanism, which has method to increment specific event with amount provided. All the SDKs for Android/iOS/C++, all they have method for incrementing event.
But REST API doesn't have this method (https://developers.google.com/games/services/web/api/events)
The only one event, which seams to be similar is record event(https://developers.google.com/games/services/web/api/events/record#auth)
but it requires user to be authenticated.
Thanks in advance.