If it is not found/covered at
Then it’s not really to be used by third parties, as it’s undocumented, unsupported and can break or change at any time.
The only v4 documented endpoints are the video upload end points. (And I think that got updated to v5 but I’ve not used them for a while and are called via kraken with a relevant header rather than the v4 path directly)
v3 and v5 are in active use
URL’s starting
as documented
or
as documented
are officially supported for third party use