But it's still incredibly beneficial to annotate the edges of your API. Not only does that quickly catch mistakes where you break the API contract, but it also

But it's still incredibly beneficial to annotate the edges of your API. Not only does that quickly catch mistakes where you break the API contract, but it also serves as built-in documentation on the shape of the data you are serving, especially if you are using a dynamic format like JSON. And that's the beauty of having static types in a language like Python: you don't have to annotate everything, and can be selective about where you apply static typing to get the most bang for your buck.