# phone_number_required

- HTTP status: 422
- Retry: No
- Execution: not started
- Admin needed: no

**Caller number must be chosen.** When `phone_number_id` is omitted, the agent's outbound number is used. This agent is assigned to several outbound numbers, so the API will not guess which one your contact should see.

## What it means

The API returns HTTP 422 with `error.code` set to `phone_number_required`. The default message is: "This agent has more than one outbound number. Choose one with phone_number_id."

## Common causes

- The agent is assigned to more than one outbound number.

## How to identify it

Check the response status (`422`) and `error.code` (`phone_number_required`). Branch on `error.code`, not on the message text: messages can be reworded, codes do not change within v1. Log `error.request_id` (also sent as the `X-Request-Id` header) so support can find the request.

## How to fix it

- Send `phone_number_id`, or assign the agent to a single outbound number in the console.

## Retry guidance

Sending the request unchanged fails the same way. Fix the cause first (see How to fix it), then send it again.

## Did anything happen?

This request was refused before any call was placed and before anything was charged.

## Idempotency

Nothing was done and the refusal is not stored under the Idempotency-Key. Fix the cause, then send the same request (with the same key if you sent one).

## Who can fix it

The developer who sends the request can fix it; no administrator action is normally needed.

## When to contact support

If the error persists after the steps above, contact [support@relationsai.com](mailto:support@relationsai.com). See [Support](/resources/support) for what to include (the `request_id`, the time in UTC, the operation, and whether you used a test or live key) and what never to send (API keys, Authorization headers, webhook signing secrets, recording links, transcripts or customer data).

## Example error response

```json
{
  "error": {
    "code": "phone_number_required",
    "message": "This agent has more than one outbound number. Choose one with phone_number_id.",
    "details": {
      "agent_id": "agent_3hT9kQ2mVx7RbN4pLc8Wz1"
    },
    "request_id": "req_beny5osdfwrs6kgzv4uhhcav",
    "retry": "no",
    "doc_url": "https://docs.relationsai.com/errors/phone_number_required"
  }
}
```

## Incorrect and corrected request

Incorrect: The agent has two outbound numbers and none was chosen.

```http
POST /v1/calls

{
  "agent_id": "agent_3hT9kQ2mVx7RbN4pLc8Wz1",
  "to": "+919000000001"
}
```

Corrected: Names the caller number with phone_number_id.

```http
POST /v1/calls

{
  "agent_id": "agent_3hT9kQ2mVx7RbN4pLc8Wz1",
  "to": "+919000000001",
  "phone_number_id": "pn_5Lq8Xc2Rk9TzW3mBv7Np4d"
}
```

## Operations that can return this error

- [`POST /calls`](/api/calls#place-a-call): Place a call
- [`POST /campaigns/{campaign_id}/start`](/api/campaigns#start-a-campaign): Start a campaign

See all codes in the [error-code reference](/fundamentals/error-codes).