Descending order does not work. Here are conversation API docs:
Both `-id` and `-latestMessageTimestamp` (and also `-latestMessageTimestampAfter`, likely typo in docs as well) will throw API error that it’s unsupported sort:
Not a big issue, I can just reverse the list, but it’s annoying that something isn’t working as per docs.
The latestMessageTimestampAfter has to be numeric representing the unix timestamp.
The “-latestMessageTimestamp” does not appear to work in conjunction with the after demarcation in any testing I did. Always returns an empty set.
You can use “-id” as the sort to get the latest threads first which is somewhat aligned with what you would want to get the most recent set first, but obviously creation is not the same as latest message timestamp
So this is not aligned. Nobody fetching history wants oldest first. Absurd. Documentation is poor.
Reversing the list is not sufficient for most applications and even if you did it’s janky af. When these new beta and other endpoints get released I am continously left scratching my head at their design decisions.
Using -id you can do continous scroll in appropriate after batches but, again, this does NOT align with latest messages first for proper sorted threads by most recent update.
Hi @nbrown8,
Thank you for posting to the Community!
I reached out to the team to see if we can get those docs updated! Will keep you posted 
Cassie, Community Manager
Hi all, I hope that you are well!
I am happy to share that the documentation has been updated! Here it is: " Conversations API - HubSpot docs ".
The Conversations API guide now specifically states: “Results are always returned in ascending order.”
Your solution of reversing the list on the client side is still the best way to achieve the order you need.
You can also submit feedback via this form: " HubSpot Developer Feedback Form ".
Thank you for flagging this for others! 
Have a lovely day!
Bérangère
