Comment by xlii

Don't fix other people problems.

If idempotent key was seen then send back response.

Clients intention is outside the scope. If contract says "idempotency on key" the idempotent response on key. If contract says "idempotent on body hash" then response on body hash (which might or might not include extra data).

APIs are contracts. Not the pinky promise of "I'll do my best guess"