In the intro to the C API (https://docs.python.org/3/c-api/intro.html#include-files), it says, "see Parsing arguments and building values for a description of this macro." There is a link which leads to ``arg.rst``, but there is no description of the macro there, just a note to include the macro like elsewhere.

I propose to remove this sentence from the docs, since it is my understanding that there is no need to document the details of why this macro must be defined, only to ensure that users define it.

Alternatively, add a description of the macro in the appropriate place in the C API docs, and fix the link in this blurb.

I'm happy to submit a documentation patch, but I'd need someone to advise on which of these options are more desired.

Looking back at this issue, I can see that there is documentation for this in the 'note' block. I'm just going to close this issue.