I am using the Entitiy Search API. What HTTP status code is returned if I issue a request but the daily limit of my access token has been reached?
HTTP/429 is used for both exceeding ones permitted request rate and for exceeding the daily permitted request count.
HTTP/503 is also noteworthy here for when the server has reached capacity and is unable to fulfil the request.
One would have to parse the response text to determine which limit is breached.
The OpenCalais User Guide §1.3 states the account limits start at 0.5-1 per second, 5,000 per day, and 100KB maximum article size.