---
title: "Make an outbound voice call. Include systemPrompt for autonomous AI conversation, omit for webhook-driven mode."
method: POST
path: "/agentphone/v1/calls"
tags: ["AgentPhone"]
---

# Make an outbound voice call. Include systemPrompt for autonomous AI conversation, omit for webhook-driven mode.

`POST /agentphone/v1/calls`

## Request

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

## Request body

- object
  - `agentId` string, required: Agent placing the call.
  - `toNumber` string, required: Recipient in E.164 format.
  - `systemPrompt` string: Instructions for autonomous mode.
  - `initialGreeting` string: First line the AI says.
  - `fromNumberId` string: Specific number to call from.
  - `voice` string: Override agent default voice.

## 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/calls/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)