AT&T SMS API

openapi: 3.0.3
info:
  title: AT&T SMS API
  description: >-
    A RESTful API enabling established businesses to broadcast SMS short code
    messages to AT&T subscribers in the United States. Supports sending to up to
    50 recipients per call and up to 1 million messaging API calls monthly.
    Includes delivery status polling, callbacks, and GSMA OneAPI-compatible endpoints.
  version: '3.0'
  contact:
    url: https://developer.att.com/support
  termsOfService: https://www.att.com/gen/general?pid=11561
  x-generated-from: documentation
  x-last-validated: '2026-04-19'
servers:
  - url: https://api.att.com
    description: AT&T API Gateway
paths:
  /oauth/v4/token:
    post:
      operationId: getAccessToken
      summary: AT&T Get OAuth Access Token
      description: >-
        Obtain an OAuth 2.0 access token using client credentials grant type.
        The token is required for all subsequent API calls.
      tags:
        - Authentication
      requestBody:
        required: true
        content:
          application/x-www-form-urlencoded:
            schema:
              $ref: '#/components/schemas/TokenRequest'
            examples:
              GetAccessTokenRequestExample:
                summary: Default getAccessToken request
                x-microcks-default: true
                value:
                  client_id: your_app_key
                  client_secret: your_app_secret
                  grant_type: client_credentials
                  scope: SMS
      responses:
        '200':
          description: Access token successfully obtained
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/TokenResponse'
              examples:
                GetAccessToken200Example:
                  summary: Default getAccessToken 200 response
                  x-microcks-default: true
                  value:
                    access_token: a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4
                    expires_in: 172800
                    refresh_token: f6e5d4c3b2a1f6e5d4c3b2a1f6e5d4c3
                    token_type: BEARER
        '400':
          description: Bad request - invalid parameters
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized - invalid credentials
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
  /sms/v3/messaging/outbox:
    post:
      operationId: sendSms
      summary: AT&T Send SMS Message
      description: >-
        Send an SMS message to one or more recipients using a registered AT&T
        short code. Supports up to 50 recipients per request and messages up to
        4096 characters. Optionally request delivery status notifications via callback.
      tags:
        - SMS Messaging
      security:
        - oauth2: [SMS]
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SendSmsRequest'
            examples:
              SendSmsRequestExample:
                summary: Default sendSms request
                x-microcks-default: true
                value:
                  outboundSMSRequest:
                    address:
                      - tel:+12125551234
                    message: Your verification code is 482910. Valid for 10 minutes.
                    notifyDeliveryStatus: true
      responses:
        '201':
          description: SMS message successfully queued for delivery
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SendSmsResponse'
              examples:
                SendSms201Example:
                  summary: Default sendSms 201 response
                  x-microcks-default: true
                  value:
                    outboundSMSResponse:
                      messageId: msg-500123
                      resourceReference:
                        resourceURL: https://api.att.com/sms/v3/messaging/outbox/msg-500123
        '400':
          description: Bad request - invalid parameters or message format
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized - invalid or expired token
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '403':
          description: Forbidden - insufficient permissions or scope
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '429':
          description: Too many requests - rate limit exceeded
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
  /sms/v3/messaging/outbox/{messageId}:
    get:
      operationId: getSmsDeliveryStatus
      summary: AT&T Get SMS Delivery Status
      description: >-
        Retrieve the delivery status of a previously sent SMS message using
        its message ID. Returns delivery status such as DeliveredToNetwork,
        DeliveredToTerminal, or DeliveryImpossible.
      tags:
        - SMS Messaging
      security:
        - oauth2: [SMS]
      parameters:
        - name: messageId
          in: path
          required: true
          description: The unique message identifier returned by the Send SMS operation
          schema:
            type: string
            example: msg-500123
      responses:
        '200':
          description: Delivery status successfully retrieved
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/DeliveryInfoResponse'
              examples:
                GetSmsDeliveryStatus200Example:
                  summary: Default getSmsDeliveryStatus 200 response
                  x-microcks-default: true
                  value:
                    deliveryInfoList:
                      deliveryInfo:
                        - address: tel:+12125551234
                          deliveryStatus: DeliveredToTerminal
                      resourceURL: https://api.att.com/sms/v3/messaging/outbox/msg-500123
        '404':
          description: Message not found
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
  /sms/v3/messaging/inbox/{registrationId}:
    get:
      operationId: getInboundSms
      summary: AT&T Get Inbound SMS Messages
      description: >-
        Poll for inbound SMS messages sent to the registered short code. Returns
        messages received since last poll. Short code registration ID is obtained
        from the AT&T developer account.
      tags:
        - SMS Messaging
      security:
        - oauth2: [SMS]
      parameters:
        - name: registrationId
          in: path
          required: true
          description: The short code registration ID from the AT&T developer account
          schema:
            type: string
            example: REG-500123
      responses:
        '200':
          description: Inbound messages successfully retrieved
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/InboundSmsResponse'
              examples:
                GetInboundSms200Example:
                  summary: Default getInboundSms 200 response
                  x-microcks-default: true
                  value:
                    inboundSMSMessageList:
                      inboundSMSMessage:
                        - messageId: msg-500456
                          message: STOP
                          senderAddress: tel:+12125551234
                          destinationAddress: '12345'
                          dateTime: '2026-04-19T14:30:00Z'
                      numberOfMessagesInThisBatch: 1
                      resourceURL: https://api.att.com/sms/v3/messaging/inbox/REG-500123
                      totalNumberOfPendingMessages: 0
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '404':
          description: Registration ID not found
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
      x-microcks-operation:
        delay: 0
        dispatcher: FALLBACK
components:
  securitySchemes:
    oauth2:
      type: oauth2
      description: AT&T OAuth 2.0 authentication using client credentials grant
      flows:
        clientCredentials:
          tokenUrl: https://api.att.com/oauth/v4/token
          scopes:
            SMS: Access to SMS messaging APIs
            MMS: Access to MMS messaging APIs
            SPEECH: Access to Speech to Text APIs
            TTS: Access to Text to Speech APIs
            STTC: Access to Speech to Text Custom APIs
            ADS: Access to Advertising APIs
  schemas:
    TokenRequest:
      type: object
      required:
        - client_id
        - client_secret
        - grant_type
        - scope
      properties:
        client_id:
          type: string
          description: The App Key from your AT&T developer account
          example: your_app_key
        client_secret:
          type: string
          description: The App Secret from your AT&T developer account
          example: your_app_secret
        grant_type:
          type: string
          description: OAuth grant type
          enum:
            - client_credentials
            - authorization_code
            - refresh_token
          example: client_credentials
        scope:
          type: string
          description: Space-separated list of API scopes (e.g. SMS, MMS, SPEECH)
          example: SMS
        code:
          type: string
          description: Authorization code (required for authorization_code grant type)
          example: auth_code_abc123
        refresh_token:
          type: string
          description: Refresh token (required for refresh_token grant type)
          example: f6e5d4c3b2a1f6e5d4c3b2a1f6e5d4c3
    TokenResponse:
      type: object
      properties:
        access_token:
          type: string
          description: OAuth access token valid for 2 days (172800 seconds)
          example: a1b2c3d4e5f6a1b2c3d4e5f6a1b2c3d4
        expires_in:
          type: integer
          description: Token expiration time in seconds (default 172800)
          example: 172800
        refresh_token:
          type: string
          description: Refresh token valid for 90 days
          example: f6e5d4c3b2a1f6e5d4c3b2a1f6e5d4c3
        token_type:
          type: string
          description: Token type (always BEARER)
          example: BEARER
    SendSmsRequest:
      type: object
      required:
        - outboundSMSRequest
      properties:
        outboundSMSRequest:
          type: object
          required:
            - address
            - message
          properties:
            address:
              type: array
              description: List of destination phone numbers in tel:+E.164 format (max 50)
              items:
                type: string
                example: tel:+12125551234
              example:
                - tel:+12125551234
            message:
              type: string
              description: SMS message text (max 4096 characters)
              example: Your verification code is 482910. Valid for 10 minutes.
            notifyDeliveryStatus:
              type: boolean
              description: If true, delivery status notifications are sent to the registered callback URL
              example: true
    SendSmsResponse:
      type: object
      properties:
        outboundSMSResponse:
          type: object
          properties:
            messageId:
              type: string
              description: Unique identifier for the sent message
              example: msg-500123
            resourceReference:
              type: object
              properties:
                resourceURL:
                  type: string
                  format: uri
                  description: URL to check delivery status of this message
                  example: https://api.att.com/sms/v3/messaging/outbox/msg-500123
    DeliveryInfoResponse:
      type: object
      properties:
        deliveryInfoList:
          type: object
          properties:
            deliveryInfo:
              type: array
              items:
                $ref: '#/components/schemas/DeliveryInfo'
            resourceURL:
              type: string
              format: uri
              description: URL of this delivery info resource
              example: https://api.att.com/sms/v3/messaging/outbox/msg-500123
    DeliveryInfo:
      type: object
      properties:
        address:
          type: string
          description: Recipient phone number
          example: tel:+12125551234
        deliveryStatus:
          type: string
          description: Current delivery status of the message
          enum:
            - DeliveredToNetwork
            - DeliveredToTerminal
            - DeliveryImpossible
            - MessageWaiting
            - DeliveryUncertain
          example: DeliveredToTerminal
    InboundSmsResponse:
      type: object
      properties:
        inboundSMSMessageList:
          type: object
          properties:
            inboundSMSMessage:
              type: array
              items:
                $ref: '#/components/schemas/InboundSmsMessage'
            numberOfMessagesInThisBatch:
              type: integer
              description: Number of messages in this response batch
              example: 1
            resourceURL:
              type: string
              format: uri
              description: URL of this inbox resource
              example: https://api.att.com/sms/v3/messaging/inbox/REG-500123
            totalNumberOfPendingMessages:
              type: integer
              description: Total number of messages waiting to be retrieved
              example: 0
    InboundSmsMessage:
      type: object
      properties:
        messageId:
          type: string
          description: Unique identifier for the inbound message
          example: msg-500456
        message:
          type: string
          description: SMS message text content
          example: STOP
        senderAddress:
          type: string
          description: Phone number of the message sender in tel:+E.164 format
          example: tel:+12125551234
        destinationAddress:
          type: string
          description: Short code that received the message
          example: '12345'
        dateTime:
          type: string
          format: date-time
          description: Date and time when the message was received
          example: '2026-04-19T14:30:00Z'
    ErrorResponse:
      type: object
      properties:
        RequestError:
          type: object
          properties:
            ServiceException:
              type: object
              properties:
                MessageId:
                  type: string
                  description: Error message ID
                  example: SVC0002
                Text:
                  type: string
                  description: Human-readable error description
                  example: Invalid input value for message part
                Variables:
                  type: string
                  description: Additional error context variables
                  example: address