---
title: "Send an SMS from an agent's phone number. First message compliance: Your initial SMS to any new contact must include (1) your brand name, (2) opt-in confirmation, and (3) opt-out instructions (e.g., \"Reply STOP to unsubscribe\"). Non-compliant first messages may be silently filtered by carriers."
method: POST
path: "/agentphone/v1/messages"
tags: ["AgentPhone"]
---

# Send an SMS from an agent's phone number. First message compliance: Your initial SMS to any new contact must include (1) your brand name, (2) opt-in confirmation, and (3) opt-out instructions (e.g., "Reply STOP to unsubscribe"). Non-compliant first messages may be silently filtered by carriers.

`POST /agentphone/v1/messages`

## Request

- Base URL: `https://api.orthogonal.com/mpp`
- URL: `https://api.orthogonal.com/mpp/agentphone/v1/messages`
- Auth: none declared
- TypeScript: <https://skmtc.dev/orthogonal/apis/orthogonal-api-marketplace/docs/agentphone/v1/messages/post.ts> (a function with typed inputs; its response is checked against the schema)

## Request body

- object
  - `agent_id` string, required: Agent sending the message.
  - `to_number` string, required: Recipient in E.164 format.
  - `body` string, required: Message text.
  - `media_url` string: URL for MMS attachment.
  - `number_id` string: Specific number to send from.

## Response `200`

Successful response

## Other responses

- `402`: Payment Required (x402 / MPP / np)

## Changes

- **2026-11-08** `857e915717f4`: 1 breaking
  - added required request body

[Operation history](https://skmtc.dev/orthogonal/apis/orthogonal-api-marketplace/changes/agentphone/v1/messages/post.md)

---

[API](https://skmtc.dev/orthogonal/apis/orthogonal-api-marketplace.md) - [All operations](https://skmtc.dev/orthogonal/apis/orthogonal-api-marketplace/llms.txt) - [OpenAPI document](https://skmtc.dev/orthogonal/apis/orthogonal-api-marketplace/revisions/fc2e1d26c8eb?raw)