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

# Post v1sms

> Send an SMS message. Starts a durable workflow for SMS delivery with retry guarantees and cost tracking.



## OpenAPI

````yaml https://api.transmit.dev/openapi.json post /v1/sms
openapi: 3.1.0
info:
  title: Transmit.dev API
  description: >-
    A powerful email API for transactional and marketing emails. Send emails
    with tracking, analytics, and webhook support.
  version: 1.0.3
servers:
  - url: https://api.transmit.dev
    description: Production server
security:
  - bearerAuth: []
tags:
  - name: Emails
    description: Email sending and management operations
  - name: SMS
    description: SMS sending and management operations with toll-free numbers
  - name: Analytics
    description: Performance analytics and metrics
  - name: Billing
    description: Credit balance and usage information
  - name: Contacts
    description: Contact management operations
  - name: Webhooks
    description: Webhook configuration and testing
paths:
  /v1/sms:
    post:
      tags:
        - SMS
      description: >-
        Send an SMS message. Starts a durable workflow for SMS delivery with
        retry guarantees and cost tracking.
      operationId: sendSms
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                from:
                  type: string
                  pattern: ^\+[1-9]\d{1,14}$
                to:
                  type: string
                  pattern: ^\+[1-9]\d{1,14}$
                body:
                  type: string
                  minLength: 1
                  maxLength: 1600
                media_urls:
                  type: array
                  items:
                    type: string
                    format: uri
              required:
                - from
                - to
                - body
      responses:
        '202':
          description: >-
            SMS accepted for processing. Message record created and workflow
            started.
          content:
            application/json:
              schema:
                type: object
                properties:
                  id:
                    type: string
                    description: SMS message ID
                  workflow_id:
                    description: Workflow ID for tracking durable execution
                    type: string
                  from:
                    type: string
                    description: Sender phone number (E.164 format)
                  to:
                    type: string
                    description: Recipient phone number (E.164 format)
                  body:
                    type: string
                    description: Message body
                  segments_count:
                    type: number
                    description: Number of SMS segments
                  credits_consumed:
                    type: number
                    description: Credits consumed for this message
                  status:
                    type: string
                    const: processing
                    description: SMS processing status
                  created_at:
                    type: string
                    format: date-time
                    pattern: >-
                      ^(?:(?:\d\d[2468][048]|\d\d[13579][26]|\d\d0[48]|[02468][048]00|[13579][26]00)-02-29|\d{4}-(?:(?:0[13578]|1[02])-(?:0[1-9]|[12]\d|3[01])|(?:0[469]|11)-(?:0[1-9]|[12]\d|30)|(?:02)-(?:0[1-9]|1\d|2[0-8])))T(?:(?:[01]\d|2[0-3]):[0-5]\d(?::[0-5]\d(?:\.\d+)?)?(?:Z))$
                    description: Creation timestamp
                required:
                  - id
                  - from
                  - to
                  - body
                  - segments_count
                  - credits_consumed
                  - status
                  - created_at
        '400':
          description: Bad request - validation error
          content:
            application/json:
              schema:
                type: object
                properties:
                  code:
                    type: string
                    description: Error code
                  message:
                    type: string
                    description: Error message
                  statusCode:
                    type: number
                    description: HTTP status code
                  details:
                    description: Additional error details
                required:
                  - code
                  - message
                  - statusCode
        '401':
          description: Authentication required
          content:
            application/json:
              schema:
                type: object
                properties:
                  code:
                    type: string
                    description: Error code
                  message:
                    type: string
                    description: Error message
                  statusCode:
                    type: number
                    description: HTTP status code
                  details:
                    description: Additional error details
                required:
                  - code
                  - message
                  - statusCode
        '403':
          description: >-
            Forbidden - from number not owned by organization, verification
            required, or account suspended
          content:
            application/json:
              schema:
                type: object
                properties:
                  code:
                    type: string
                    description: Error code
                  message:
                    type: string
                    description: Error message
                  statusCode:
                    type: number
                    description: HTTP status code
                  details:
                    description: Additional error details
                required:
                  - code
                  - message
                  - statusCode
        '422':
          description: Validation error - invalid E.164 phone number format
          content:
            application/json:
              schema:
                type: object
                properties:
                  code:
                    type: string
                    description: Error code
                  message:
                    type: string
                    description: Error message
                  statusCode:
                    type: number
                    description: HTTP status code
                  details:
                    description: Additional error details
                required:
                  - code
                  - message
                  - statusCode
        '429':
          description: Rate limit exceeded or insufficient credits
          content:
            application/json:
              schema:
                type: object
                properties:
                  code:
                    type: string
                    description: Error code
                  message:
                    type: string
                    description: Error message
                  statusCode:
                    type: number
                    description: HTTP status code
                  details:
                    description: Additional error details
                required:
                  - code
                  - message
                  - statusCode
        '500':
          description: Internal server error
          content:
            application/json:
              schema:
                type: object
                properties:
                  code:
                    type: string
                    description: Error code
                  message:
                    type: string
                    description: Error message
                  statusCode:
                    type: number
                    description: HTTP status code
                  details:
                    description: Additional error details
                required:
                  - code
                  - message
                  - statusCode
components:
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      bearerFormat: API Key
      description: >-
        Enter your API key with 'tx_' prefix. Get your API key from the
        dashboard.

````