I don't know what's authoritative, but I can share that it has helped with devpi or bandersnatch having bugs in the past.
Bandersnatch sends something like:
"bandersnatch/2.1.2 (cpython 3.6.3-candidate1, Linux x86_64)"
A few quick questions about pip/pypi and user agent strings.
Does PyPi/Warehouse do anything with the user agent string or does it just go into the BigQuery system?
What elements of the user agent string are used?
Is the pip source code the reference document or is there a separate specification?
Distutils-SIG maillist - Distutils-SIG@python.orghttps://mail.python.org/mailman/listinfo/distutils-sig