{
  "@context": "https://www.w3.org/ns/activitystreams",
  "id": "http://...",
  "type": "Add",
  "actor": 'http://sally.example.org',
  "target": "http://collection...",
  "object": {
    "type": "Note",
    "id": "http://...",
    "content": "..."
  }
}