Default docstring from PyCharm automatically creates template with Args: and Returns: sections. However I have observed that this prompts people to say obvious things, frequently just stating the variable name without underscores (if name was chosen well).
My first external source was the source code of mypy, a project where GvR is one of the developers (therefore I expect it to be in line with best practices). Documentation there is plain english stating the purpose and further details, but everything about args and return is only in the (typed) method signature and var names.
However, PEP257 states: The docstring for a function or method should summarize its behavior and document its arguments, return value(s), side effects, exceptions raised, and restrictions on when it can be called (all if applicable). Optional arguments should be indicated. It should be documented whether keyword arguments are part of the interface.
Result is currently that I am trying to use best judgement on where we can make useful comments including Args: Returns: and where it is redundant, but this makes it look very diverse and unpredictable.
Background: I am trying to establish best practices for comments in a small python project (5 people).