I'm currently trying to understand Etsy's Open API v3, and I came across a relatively recent Google Groups conversation post that asks a question about a public API endpoint (/api/v3/ajax/bespoke...). I can't seem to find any official documentation about these "public" endpoints anywhere, but they seem to be working.
Can these be used regularly or is Etsy not documenting them for a reason?
The Ajax API was meant for internal use. I would not recommend using it, as it is limited and could disappear at any point. It is also worth noting that while it is 'v3', it is not related to their Open API v3.