Chat Transcript API

I've been looking through the chat API's and don't see a way to get the messages associated with a chat.  I see that a chat has engagements, and the engagements have counts of user and agent messages, but the actual message text does not seem to be available.  I'd like to ultimately create a transcript from a given chat.

There appear to be ways to manually export a transcript, and also pipe a transcript to an email address, but API access doesn't seem available.

Any help is appreciated.