List endpoints return the same envelope:

{
  "count": 50,
  "limit": 50,
  "next_page_token": "eyJwayI6...",
  "messages": [ ... ]
}

curl "https://api.carlyemail.com/v0/inboxes/$INBOX_ID/messages?limit=50&page_token=$TOKEN" \
  -H "Authorization: Bearer $CARLYEMAIL_API_KEY"

Default page size is 50, maximum 200.

Why there is no total

There is no total, no offset and no arbitrary sort_by, and that is not an oversight. Counting every match means reading every match, which is a query whose cost grows with your mailbox rather than with your page. The API deliberately promises nothing it cannot serve cheaply at any size.

Use ascending to flip the direction. The token encodes position, so pages stay consistent while you walk them even as new mail arrives.