here's the 'document' you get back from get

{
  key: MessageId,
  title: String,
  startDateTime: {
    epoch: UnixTime,
    tz: String                 // *
  },
  description: String,
  location: String,
  image: {
    link: Blob,
    name: String,             // *
    size: Integer,            // *
    type: MimeTypeString      // *
  },
  images: [ Image, Image, ... ] // Objects of same form as image property
  attendees: [ FeedId, FeedId, ... ]
}

To this I'm also going to add:

• heads : sometimes it's useful to have access to the most recent messages in the document/ thread histroy (e.g. for populating the branch attribute on messages)
• thread : all the backlinks in causal order (including posts and whatever else)