How to arbitrarily control MWI through ARI?

Thank you for providing a link to the documentation.

How do I create a mailbox?

This post[1] says that ARI cannot query app_voicemail.

ari.mailboxes().update("5000", 0, 0);

Updating a mailbox with /mailboxes/{mailboxName} (which will implicitly create one)
returns mailbox not found

It was my understanding that I could call /mailboxes/{mailboxName} with the update message count arguments and it would update an extension that had its voicemail turned on in my PBX. I now think I am missing a part of how mailboxes are different then voicemails.

[1] Cant list mailboxes using ARI