A simple example comes from the article itself. Parameter 'strength', the strength of the frognication. What is the range of that? Is it 0 to max int? min int to max int? 1-100?

(A real-life example would be a function that outputs an image in JPEG or PNG and takes a quality parameter. I notice that within the same library often one type of image wants 1-100 where another type wants a different scale, like 0.0 - 1.0. The parameters have the same name.)

This is not something that can be checked by most type systems. Therefore it needs to be in the documentation.