Send a message to many creators at once

Queues one message for the audience and answers 202 with the broadcast's id and reach; the messages then go out in the background. The creators, campaigns and all audiences send it as a separate direct message to each creator (at most 500), into the existing conversation or a new one; groups posts it once in each selected group chat (at most 50). Only creators who can receive messages are reached: they joined your organization or hold a pending invitation, and selecting a creator who does not is refused. broadcastId is your idempotency key: repeating a request with the same id and payload answers 202 again and only sends what is still missing, while the same id with a different message or audience is refused (400). Each member can start 10 broadcasts per hour (429). Broadcasts carry text only. Every message fires a chat.message.sent webhook event carrying the broadcastId, which is how to follow delivery.