Message Events - Mint Starter Kit

Events acknowledging receipt of a message.

`MESSAGE_RECEIVED`

Sent after the server accepts the user’s message.

{
  "type": "MESSAGE_RECEIVED",
  "eventId": "evt_1",
  "threadId": "thread_456",
  "requestId": "req_1",
  "eventMessage": {
    "agent": null,
    "content": "Hi what can you do for me",
    "collaborationId": null,
    "activeAssistantCollaborationRequired": null,
    "toolExecutionApprovalRequest": null,
    "timestamp": "2025-08-12T00:00:00"
  }
}