After rDWUI0b68ae8fe9d0 we can now specify the type of optional parameters in docstring of API endpoints. That information, however, is not rendered, and all types are rendered as "string". See for instance http://127.0.0.1:6543/api/1/origin/visits/ (in the development version) where last_visit and per_page are rendered as "string" even if they are declared to be "int".
They should be rendered as integers, as it happen for arguments.