> ## Documentation Index > Fetch the complete documentation index at: https://help.withallo.com/llms.txt > Use this file to discover all available pages before exploring further. # Send SMS > Send an SMS message to a US phone number using one of your Allo phone numbers. The recipient must be in the same country as your Allo number. This endpoint is for sending SMS from US Allo phone numbers. For sending SMS in France, see [Send SMS (France)](/en/v2/api-reference/sms/send-sms-france). ## OpenAPI ````yaml POST /v1/api/sms openapi: 3.0.3 info: title: Allo API description: >- Allo API provides programmatic access to your Allo account, allowing you to manage webhooks, retrieve calls and contacts, and send SMS messages. All requests to `/v1/api/**` endpoints automatically go through quota checking and scope validation. version: 1.0.0 contact: name: Allo Support servers: - url: https://api.withallo.com description: Production server security: [] tags: - name: Summary Templates description: >- Manage call summary templates that control how AI-generated call summaries are structured for your team. - name: Webhooks description: >- Manage webhook endpoints to receive real-time notifications about events in your Allo account. Each endpoint subscribes to one or more event topics and is verified with a signing secret. - name: Calls description: >- Retrieve and search call records with filtering and pagination. Filter calls by your Allo phone number. - name: Contacts description: >- Search and retrieve contact information with sorting and pagination. Includes engagement level tracking. - name: SMS description: Send SMS messages to phone numbers using your Allo numbers. - name: Phone Numbers description: Retrieve information about your Allo phone numbers. - name: Analytics description: Pre-computed call metrics, team performance, and outbound dial funnel - name: CRM description: Manage people, companies, and deals in your CRM. paths: /v1/api/sms: post: tags: - SMS summary: Send SMS (US) description: >- Send an SMS message to a US phone number using one of your Allo phone numbers. The recipient must be in the same country as your Allo number. operationId: sendSMS requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/SendSMSRequest' example: from: '+1234567890' to: '+0987654321' message: Hello, this is a test message responses: '200': description: SMS sent successfully content: application/json: schema: $ref: '#/components/schemas/SendSMSResponse' example: data: from_number: '+1234567890' sender_id: null to_number: '+0987654321' type: OUTBOUND content: Hello, this is a test message start_date: '2024-01-15T10:30:00' '400': description: Bad request content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' examples: fromNumberNotFound: summary: From number not found value: code: FROM_NUMBER_NOT_FOUND details: null invalidToNumber: summary: Invalid to number value: code: INVALID_TO_NUMBER details: null toNumberCountryMismatch: summary: Country mismatch value: code: TO_NUMBER_COUNTRY_MISMATCH details: null invalidLength: summary: Invalid message length value: code: INVALID_LENGTH details: null providerNotSupported: summary: Provider not supported value: code: PROVIDER_NOT_SUPPORTED details: null '401': $ref: '#/components/responses/Unauthorized' '403': $ref: '#/components/responses/Forbidden' '429': $ref: '#/components/responses/TooManyRequests' security: - SmsAuth: [] components: schemas: SendSMSRequest: type: object description: Request body for sending an SMS message (US) required: - from - to - message properties: from: type: string description: Your Allo phone number (must be owned by your account) example: '+1234567890' to: type: string description: Recipient phone number (E.164 format, same country as 'from') example: '+0987654321' message: type: string description: Message content minLength: 1 maxLength: 1000 example: Hello, this is a test message SendSMSResponse: type: object description: Standard response wrapper for sent SMS properties: data: $ref: '#/components/schemas/TextMessageApiResponse' ErrorResponse: type: object properties: code: type: string description: Error code identifying the type of error details: type: array nullable: true items: $ref: '#/components/schemas/ErrorDetail' description: Additional error details, or null if not applicable TextMessageApiResponse: type: object description: Sent SMS message details properties: from_number: type: string nullable: true description: >- Phone number that sent the message. Null when sender_id is used instead. example: '+1234567890' sender_id: type: string nullable: true description: >- Sender ID used for the message (alphanumeric identifier). Only populated when sending with a verified Sender ID (e.g., for France SMS). Null when from_number is used. example: MyCompany to_number: type: string description: Phone number that received the message example: '+0987654321' type: type: string enum: - OUTBOUND description: Direction of the message (always OUTBOUND for sent messages) content: type: string description: Content of the SMS message example: Hello, this is a test message start_date: type: string format: date-time description: When the message was sent example: '2024-01-15T10:30:00' ErrorDetail: type: object properties: message: type: string field: type: string responses: Unauthorized: description: Unauthorized - Invalid or missing API key content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: code: API_KEY_INVALID details: null Forbidden: description: Forbidden - API key lacks required scope content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: code: API_KEY_INSUFFICIENT_SCOPE details: - message: required=CONTACTS_READ field: scope TooManyRequests: description: Too Many Requests - Rate limit exceeded content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' example: code: API_KEY_QUOTA_EXCEEDED details: - message: limit=1000;type=DAILY;reset_in=3600 field: DAILY securitySchemes: SmsAuth: type: apiKey in: header name: Authorization description: 'Scope needed: `SMS_SEND`' ````