{
  "message_type": "conversation",
  "event_type": "conversation.echo",
  "conversation_id": "c123456",
  "properties": {
    "modality": "text",
    "text": "Hey there Tim, long time no see!",
    "audio": "base64-encoded-audio",
    "sample_rate": 24000,
    "inference_id": "inference-id-123",
    "done": "true"
  }
}