typing.Callable allows you to create annotations for limited set of functions. In particularly it does not support optional or keyword arguments. In general case you need to create a protocol with the __call__ method with a specific signature. I tried to implement the Mark Shannon's idea about a decorator which converts a function into corresponding type, but failed with this. Seems my skills are not enough for this. Use case: @callable_type def Func(x: int) -> str:     pass def func(x: int) -> str:     return chr(x) func2: Func = func I tried: def callable_type(func: Callable[P, T]): class result(Protocol): def __call__(self, /, *args: P.args, **kwargs: P.kwargs) -> T: pass return result but it does not work, How can this be implemented? It would be very useful feature which we would use on work a lot.