Messages

Send a text or attachment to a group chat

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Routes an outbound message to an existing group chat. Supports text and media attachments. If the group cannot be resolved directly, the agent falls back to resolving it from its participants. Set force=true to always use the participant resolution path.

Authentication

X-App-Idstring

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

Idempotency-KeystringOptional

Request

This endpoint expects an object.
groupIdstringRequired
Group chat identifier. If it is invalid or stale, the agent resolves the chat from its participants.
fromstringOptional

Optional: if not provided, it is resolved automatically. Cannot override an existing group mapping.

textstringOptional
attachmentslist of stringsOptional
Array of public URLs of attachments
status_callbackstringOptionalformat: "uri"
Optional status callback URL
participantslist of stringsOptional

Optional participant handles (E.164 phones or emails). Used to resolve the chat when the group identifier is missing or stale, and for the force flow.

forcebooleanOptional
If true, always resolve the chat from its participants before sending, instead of sending directly by group identifier.

Response

Completed by agent
okboolean
dataobject

Endpoint-specific payload wrapped in a standard success envelope.

metaobject

Errors

400
Bad Request Error
401
Unauthorized Error
409
Conflict Error
429
Too Many Requests Error
500
Internal Server Error
503
Service Unavailable Error
504
Gateway Timeout Error