Send Instance Message

curl --request POST \
  --url https://api.example.com/agents/instances/{instance_id}/messages \
  --header 'Content-Type: application/json' \
  --data '
{
  "message": "<string>",
  "session_id": "<string>"
}
'

{
  "detail": [
    {
      "loc": [
        "<string>"
      ],
      "msg": "<string>",
      "type": "<string>",
      "input": "<unknown>",
      "ctx": {}
    }
  ]
}