I find the biggest win about API first development is it forces discipline upon you. I find I can get most of the benefits if I code in a disciplined fashion.

I find the biggest win about API first development is it forces discipline upon you. I find I can get most of the benefits if I code in a disciplined fashion. It's usually not easy though. In many ways, I find API first development most useful in languages such as python, which lacks the idea of an interface. Similarly, I find interfaces not much more than yet another tool that forces discipline upon you. It seems like as we develop these abstractions which increasingly force more discipline upon us we forget that classes and functions are supposed to be abstractions themselves. We are supposed to be relying on the interface of those classes and functions, not the actual implementations, even if the class itself doesn't use the interface keyword. One of the oft maligned issues of c++ is the .h file. I rather like them though. They're a constant reminder that "this is all you should know". It becomes obvious when you add cruft onto it because you don't have that cruft obscured by hundreds of lines of implementation. It's much more difficult to notice it in languages where the implementation of a class or module is present alongside its interface.