Providing a client or library is great, but serves to shift the actual API to be that which the client or library provides. Ultimately there is some interface

Providing a client or library is great, but serves to shift the actual API to be that which the client or library provides. Ultimately there is some interface between what you provide and your customer. That's the point you need to make as well understood as possible. A clean, intuitive interface and good documentation are both valuable in making it understood.