Do not make bulk requests without prior approval. You may be banned from this service.
Using unrecognised services is undefended behaviour, you should always check the list of services before you start making requests.
Errors returned from /api/... urls are json objects with at least the following keys: {"error": true, "status": 000, "description": "Possibly helpful message."}
Unless the backend server is down, then a generic 502 page will be returned.