API usability is not different than application usability. A good application must be designed for the best possible user experience. An Application Programming Interface must be as well.
So next time you are creating that interface to expose to a consumer regardless if that will be the lead of your country or a software developer work *with* your consumer(s) to make sure you get it right.
Separation Of Concerns (SoC) helps on that. Even if you have an all star team where everybody does from A to Z in the SDLC you might end up with greatest results if you divide the work and rotate the team through the different concerns. You will naturally avoid violation of SoC.