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POST
Create a message

Authorizations

Authorization
string
header
required

Accepts either a raw API key or Bearer <key>.

Headers

revision
string

Optional dated API revision for the request. Must use YYYY-MM-DD format.

Pattern: ^\d{4}-\d{2}-\d{2}$
Example:

"2026-03-01"

Path Parameters

broadcast_id
integer
required

Broadcast ID.

Body

application/json

Create an additional message (A/B arm) on a draft broadcast. The arm is cloned from the control message's default content (subject, body, sender); supplied fields override the clone. name, position, and other derived/audience fields are rejected with 422 Validation error.

from
string | null

Sender email address (email channel). Must match an existing verified sender for the project, otherwise 422. Defaults to the cloned control sender.

reply_to
string | null
content
object

Optional overrides for the cloned default content.

Response

Broadcast message created.

One message (A/B test arm) of a broadcast. from/reply_to are email-only sender fields and are null for SMS/push messages.

id
integer
required
broadcast_id
integer
required
position
integer
required
name
string | null
required

Server-generated message name, for example Control or Variation A.

active
boolean
required
from
string | null
required

Sender email address (email messages only).

reply_to
string | null
required

Reply-to email address (email messages only).

created_at
string<date-time>
required
updated_at
string<date-time>
required