Create a new group chat and send an intro message
Creates a new iMessage group from participant handles and sends the intro message. Returns as soon as the Mac agent confirms the UI create+send. groupId is best-effort and may be null — for follow-up messages, call /sendGroupMessage with the same participants and force=true (the agent resolves the chat from participants).
Authentication
Your MessageBlue App ID, sent in clear on every request. It is paired with request signing: each request is also signed with your App Secret (see the Authentication tag). The App Secret itself is NEVER transmitted — it is only the HMAC signing key.
Headers
Optional: replays return the same cached create result for 24h.
Request
At least two distinct phone numbers (E.164) or email handles.
Optional agent to create the group from. If omitted, least-mapped available agent is chosen.
Response
Endpoint-specific payload wrapped in a standard success envelope.