Your documentation is great! You've got straightforward authentication, prominent curl examples, expected responses, clear-cut explanations of expected inputs... I think your API looks fun and easy to use! I don't send physical mail, but if I did and tried your API, I would probably get in trouble for mail-bombing hate mail to my elected officials.

Hey, wait a minute! Those examples are using test credentials... Your API responds to those curl calls with real output, and the output matches what your documentation says it should be. Okay, that is awesome! Also when I force myself to get rate-limited, my requests fail gracefully with a "429 Too Many Requests" and a descriptive error, which is refreshing. Nice API!