AT&T SMS Messaging API
The SMS Messaging API from AT&T — 3 operation(s) for sms messaging.
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OpenAPI Specification
openapi: 3.2.0
info:
title: AT&T SMS SMS Messaging 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
tags:
- name: SMS Messaging
paths:
/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:
schemas:
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
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
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
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
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'
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
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