Especially when it comes to API's, documentation is 100% part of the engineering. Very few non-trivial API's are self-explanatory because you have to map a comp

Especially when it comes to API's, documentation is 100% part of the engineering. Very few non-trivial API's are self-explanatory because you have to map a complex problem space to an imperfect engineering-focused formulation of the problem domain, and the mapping usually involves introducing design patterns to make the problem space easier to manage in code.