APIs, whether on the web or in a library of local code, are what programmers interact with day in and day out. The term "API" is loose and all-encompassing, and while programmers may not be able to define exactly what one is, they know a bad one when they see it. This talk explores the interaction design of APIs, particularly through the lens of the speaker's experience evolving the popular Twitter API. The speaker will argue for the notion of a "humane API", one derived from simplicity, "explorability", and consistency