> ## Documentation Index
> Fetch the complete documentation index at: https://www.voiceflow.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Outbound calling

> Programmatically trigger your agent to call any phone number.

> [!NOTE]
>
> In some regions, automated outbound calls without consent may violate local regulations. You are responsible for ensuring compliance with all relevant laws.

Outbound calling lets your agent initiate phone calls programmatically. You can use this to automate voice interactions like welcome calls, appointment reminders, or follow-ups, triggered from tools like Zapier or your own backend scripts.

Outbound calling is supported for Twilio, Vonage, and Telnyx phone numbers. Voiceflow phone numbers currently don't support outbound calling.

## Making an outbound call

To trigger an outbound call, send a `POST` request to your agent's outbound API endpoint. You can find this endpoint by opening **Phone numbers** in the sidebar, then clicking **View** in the **Outbound call API** column for your number.

<video autoPlay muted loop playsInline src="https://mintcdn.com/voiceflow-009a8802/s3P1FU2SwfLb9qjL/videos/outbound.mp4?fit=max&auto=format&n=s3P1FU2SwfLb9qjL&q=85&s=8533207c888584bd071a95d42e2391dc" />

The modal displays a ready-to-use curl command with your agent's endpoint and required headers. You can also test the call directly from this modal by entering a phone number and clicking **Call**.

## API reference

### Endpoint

```
POST https://runtime-api.voiceflow.com/v1/phone-number/<PHONE_NUMBER_ID>/outbound
```

### Headers

| Header | Value |
| - | - |
| `Authorization` | Your [Dialog Manager API key](https://docs.voiceflow.com/reference/how-to-get-your-voiceflow-project-api-key) |
| `Content-Type` | `application/json` |

### Request body

```json theme={null}
{
  "to": "+15551234567",
  "variables": {
    "user_name": "Jane",
    "account_type": "Premium"
  },
  "amd": true
}
```

| Field | Description |
| - | - |
| `to` | The phone number to call in E.164 format (eg: `+15551234567`). |
| `variables` | Optional. A JSON object containing variables to inject when the call starts. |
| `amd` | Optional. Set to `true` to enable answering machine detection. |

## Concurrency limits

Outbound calls share the same concurrency pool as inbound calls. The number of simultaneous calls you can make depends on your [plan limits](https://voiceflow.com/pricing).


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