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

# Send a message to a conversation

> Send an outbound message (text + optional attachments) on the conversation's current channel. `isInternal: true` posts a whisper note visible only to agents.



## OpenAPI

````yaml /api-reference/openapi.yaml post /api/conversation/{conversationId}/send-message
openapi: 3.0.3
info:
  title: Tether Relay and Tether API
  version: 1.0.0
  description: >-
    Route-derived OpenAPI contract generated from tether-relay backend sources.
    Regenerate with scripts/sync-openapi-from-backend.mjs.
servers:
  - url: https://your-instance.example.com
    description: Production
  - url: http://localhost:2212
    description: Local API service
security: []
tags:
  - name: AI
  - name: Applications
  - name: Approval
  - name: Auth
  - name: Automations
  - name: Calls
  - name: Campaigns
  - name: Contact Analytics
  - name: Contact Metrics
  - name: Contact Notes
  - name: Contacts
  - name: Conversation Monitor
  - name: Conversations
  - name: Departments
  - name: Email
  - name: Escalation Dashboard
  - name: Event Logs
  - name: Google Sheets
  - name: Marketplace
  - name: Messages
  - name: Notification Sounds
  - name: Notifications
  - name: Org Snapshots
  - name: Organizations
  - name: Outreach
  - name: Outreach Metrics
  - name: Outreach Sources
  - name: Pipelines
  - name: Processes
  - name: Prompts
  - name: Reminders
  - name: Sms
  - name: Templates
  - name: Traces
  - name: Training
  - name: Upload
  - name: User Snapshots
  - name: Users
  - name: Vertical
  - name: Webchats
  - name: Webhook
paths:
  /api/conversation/{conversationId}/send-message:
    post:
      tags:
        - Conversations
      summary: Send a message to a conversation
      description: >-
        Send an outbound message (text + optional attachments) on the
        conversation's current channel. `isInternal: true` posts a whisper note
        visible only to agents.
      operationId: post_conversation_send_message
      parameters:
        - in: path
          name: conversationId
          required: true
          schema:
            type: string
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SendMessageToConversationRequest'
      responses:
        '200':
          description: Message sent
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SendMessageToConversationResponse'
        '400':
          description: Validation error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/LegacyErrorResponse'
        '403':
          description: Forbidden
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/LegacyErrorResponse'
        '404':
          description: Conversation not found
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/LegacyErrorResponse'
      security:
        - bearerAuth: []
components:
  schemas:
    SendMessageToConversationRequest:
      type: object
      properties:
        body:
          type: string
          description: Message content
        attachments:
          type: array
          items:
            type: object
            properties:
              url:
                type: string
              filename:
                type: string
              contentType:
                type: string
            required:
              - filename
            additionalProperties: true
        isInternal:
          type: boolean
          description: Whether this is an internal/whisper message
      required:
        - body
      additionalProperties: true
      example:
        body: Thanks for confirming, we'll follow up tomorrow.
        attachments:
          - url: https://r2.example.com/messages/.../quote.pdf
            filename: quote.pdf
            contentType: application/pdf
        isInternal: false
    SendMessageToConversationResponse:
      type: object
      properties:
        success:
          type: boolean
        message:
          type: object
          additionalProperties: true
      additionalProperties: true
      example:
        success: true
        message:
          _id: 67e0a0b0c0d0e0f0a0b0c0d1
          body: Thanks for confirming, we'll follow up tomorrow.
          direction: outbound
          senderType: HUMAN
          createdAt: '2026-05-18T14:15:00.000Z'
    LegacyErrorResponse:
      type: object
      properties:
        error:
          type: string
        message:
          type: string
        data: {}
      additionalProperties: true
      example:
        error: Attachment not found
        message: Attachment not found
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: JWT

````