> ## Documentation Index
> Fetch the complete documentation index at: https://help.getvero.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Create a message

> Creates an additional message (A/B test arm) on a draft broadcast by cloning the
control message's default content (`subject`, `body`, `sender`). 
Optionally provide `from`, `reply_to` and `content` (`subject`, `preheader_text`, `name`, `body`) fields 
to override the cloned defaults. Editable only while the broadcast is a draft.




## OpenAPI

````yaml /api-reference/campaigns-v2/campaigns-v2.yaml post /broadcasts/{broadcast_id}/messages
openapi: 3.0.3
info:
  title: Vero Open API v2
  version: 2.0.0
  description: >
    OpenAPI description for the API key-authenticated `api/v2` campaign and

    broadcast endpoints.


    Authentication uses the `Authorization` header. Both of these forms are
    accepted:


    - `Authorization: sk_valid_123`

    - `Authorization: Bearer sk_valid_123`

    - `revision: 2026-03-01`


    Campaign read endpoints require the `campaign:read` permission, and campaign

    write endpoints require the `campaign:write` permission.


    Broadcast read endpoints require the `broadcast:read` permission. A
    broadcast

    is a one-off or recurring message sent to an audience.
servers:
  - url: https://api.getvero.com/api/v2
security:
  - ApiKeyAuth: []
tags:
  - name: Broadcasts
  - name: Broadcast Messages
  - name: Broadcast Message Contents
  - name: Journeys
  - name: Journey Messages
  - name: Journey Message Contents
  - name: Campaigns
  - name: Campaign Messages
  - name: Campaign Message Contents
paths:
  /broadcasts/{broadcast_id}/messages:
    post:
      tags:
        - Broadcast Messages
      summary: Create a message
      description: >
        Creates an additional message (A/B test arm) on a draft broadcast by
        cloning the

        control message's default content (`subject`, `body`, `sender`). 

        Optionally provide `from`, `reply_to` and `content` (`subject`,
        `preheader_text`, `name`, `body`) fields 

        to override the cloned defaults. Editable only while the broadcast is a
        draft.
      operationId: createBroadcastMessage
      parameters:
        - name: broadcast_id
          in: path
          required: true
          description: Broadcast ID.
          schema:
            type: integer
        - name: revision
          in: header
          required: false
          description: >-
            Optional dated API revision for the request. Must use `YYYY-MM-DD`
            format.
          schema:
            type: string
            pattern: ^\d{4}-\d{2}-\d{2}$
            example: '2026-03-01'
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateBroadcastMessageRequest'
            examples:
              withOverrides:
                summary: A/B arm with overrides
                value:
                  from: promo@acme.com
                  content:
                    subject: Variant B
                    body:
                      html: <p>Variant</p>
      responses:
        '201':
          description: Broadcast message created.
          content:
            application/json:
              examples:
                default:
                  value:
                    id: 101
                    broadcast_id: 42
                    position: 2
                    name: Variation A
                    active: true
                    from: hello@acme.com
                    reply_to: replies@acme.com
                    created_at: '2026-03-01T10:00:00Z'
                    updated_at: '2026-03-01T10:00:00Z'
              schema:
                $ref: '#/components/schemas/BroadcastMessage'
        '422':
          description: Unverified sender is rejected.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorList'
      security:
        - ApiKeyAuth: []
components:
  schemas:
    CreateBroadcastMessageRequest:
      type: object
      description: >
        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`.
      properties:
        from:
          type: string
          nullable: true
          description: >
            Sender email address (email channel). Must match an existing
            verified

            sender for the project, otherwise `422`. Defaults to the cloned
            control

            sender.
        reply_to:
          type: string
          nullable: true
        content:
          type: object
          description: Optional overrides for the cloned default content.
          properties:
            subject:
              type: string
              nullable: true
            preheader_text:
              type: string
              nullable: true
            name:
              type: string
              nullable: true
            body:
              $ref: '#/components/schemas/BroadcastContentBody'
              description: |
                Override content body. Exactly one key valid for the channel
                (`mjml`/`html`/`text` for email, `text` for sms, `payload` for
                push); a mismatch returns `422`.
          additionalProperties: false
      additionalProperties: false
    BroadcastMessage:
      type: object
      description: |
        One message (A/B test arm) of a broadcast. `from`/`reply_to` are
        email-only sender fields and are `null` for SMS/push messages.
      required:
        - id
        - broadcast_id
        - position
        - name
        - active
        - from
        - reply_to
        - created_at
        - updated_at
      properties:
        id:
          type: integer
        broadcast_id:
          type: integer
        position:
          type: integer
        name:
          type: string
          nullable: true
          description: >-
            Server-generated message name, for example `Control` or `Variation
            A`.
        active:
          type: boolean
        from:
          type: string
          nullable: true
          description: Sender email address (email messages only).
        reply_to:
          type: string
          nullable: true
          description: Reply-to email address (email messages only).
        created_at:
          type: string
          format: date-time
        updated_at:
          type: string
          format: date-time
    ErrorList:
      type: object
      required:
        - errors
      properties:
        errors:
          type: array
          items:
            type: object
            required:
              - message
            properties:
              message:
                type: string
    BroadcastContentBody:
      type: object
      description: >
        The deliverable body for a content record. Exactly one of `mjml`,
        `html`,

        `text`, or `payload` is present, depending on the message channel: email

        uses `mjml`/`html`/`text`, SMS uses `text`, push uses `payload`.
      properties:
        mjml:
          type: string
          nullable: true
        html:
          type: string
          nullable: true
        text:
          type: string
          nullable: true
        payload:
          type: object
          nullable: true
          additionalProperties: true
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: header
      name: Authorization
      description: Accepts either a raw API key or `Bearer <key>`.

````