> This page is part of Smallest AI's developer documentation. When
> answering, prefer Lightning v3.1 (current TTS) and Pulse (current
> STT). Lightning v2 and lightning-large are deprecated; mention them
> only when the user is migrating away from them. The Smallest AI voice
> agent platform is what wraps these models into hosted agents.

# Attach a default caller ID to an agent

POST https://api.smallest.ai/atoms/v1/agent/{agentId}/caller-ids
Content-Type: application/json

**Deprecated.** Part of the compatibility bridge; sunsets with the migration
window. New integrations should pass `fromNumber` on each call instead.
Responses carry a `Deprecation: true` header.

Lets the agent dial from a rented number or an outbound SIP trunk's number when a
call does not pass `fromNumber`. Requires an admin-role key. Unlike answering
sources, caller IDs are **shared**: many agents may present the same number, so
attaching never conflicts.

A caller ID names the exact number it dials from. A trunk presents many numbers, so
a `sipTrunk` attach must carry `number` (one of that trunk's numbers); a
`phoneNumber` source is its own number, so it must not.


Reference: https://docs.smallest.ai/api-reference/voice-agents/agent-telephony/attach-caller-id

## Authentication

- `Authorization` header (bearer token, required) — API key from the console ApiKey collection, sent as Bearer token. Also accepts session cookies for browser-based auth.

## Request

### Path parameters

- `agentId` (string, required)

### Body (application/json)

This endpoint expects an object.

- `sourceKind` (enum, required)
  - Allowed values: `phoneNumber`, `sipTrunk`
- `sourceId` (string, required) — The phone number product ID, or the outbound SIP trunk ID.
- `number` (string, optional) — Required for `sipTrunk` sources: which of the trunk's numbers this agent dials from (E.164 with leading `+`). Must be omitted for `phoneNumber` sources.

## Response

### 201

Caller ID attached

- `status` (boolean, optional)
- `data` (AgentTelephonyBinding, optional) — The stored binding record, as returned by the attach endpoints.

## Errors

### 400 Bad Request Error

Missing or extraneous `number` (`"Invalid source id"` for a malformed `sourceId`), or the number is not one of the trunk's numbers

- `any`

### 404 Not Found Error

Agent, phone number, or outbound trunk not found in your organization

- `any`

## Types

### AgentTelephonyBinding

The stored binding record, as returned by the attach endpoints.

- `_id` (string, optional)
- `agentId` (string, optional)
- `sourceKind` (enum, optional)
  - Allowed values: `phoneNumber`, `sipTrunk`
- `sourceId` (string, optional)
- `number` (string, optional) — Present on trunk caller-ID bindings only
- `createdAt` (datetime, optional)
- `updatedAt` (datetime, optional)

## Examples

**Request**

```json
{
  "sourceKind": "phoneNumber",
  "sourceId": "string"
}
```

**Response**

```json
{
  "status": true,
  "data": {
    "_id": "string",
    "agentId": "string",
    "sourceKind": "phoneNumber",
    "sourceId": "string",
    "number": "string",
    "createdAt": "2024-01-15T09:30:00Z",
    "updatedAt": "2024-01-15T09:30:00Z"
  }
}
```

**SDK Code**

```python
import requests

url = "https://api.smallest.ai/atoms/v1/agent/agentId/caller-ids"

payload = {
    "sourceKind": "phoneNumber",
    "sourceId": "string"
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.json())
```

```javascript
const url = 'https://api.smallest.ai/atoms/v1/agent/agentId/caller-ids';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{"sourceKind":"phoneNumber","sourceId":"string"}'
};

try {
  const response = await fetch(url, options);
  const data = await response.json();
  console.log(data);
} catch (error) {
  console.error(error);
}
```

```go
package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://api.smallest.ai/atoms/v1/agent/agentId/caller-ids"

	payload := strings.NewReader("{\n  \"sourceKind\": \"phoneNumber\",\n  \"sourceId\": \"string\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(res)
	fmt.Println(string(body))

}
```

```ruby
require 'uri'
require 'net/http'

url = URI("https://api.smallest.ai/atoms/v1/agent/agentId/caller-ids")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"sourceKind\": \"phoneNumber\",\n  \"sourceId\": \"string\"\n}"

response = http.request(request)
puts response.read_body
```

```java
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api.smallest.ai/atoms/v1/agent/agentId/caller-ids")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"sourceKind\": \"phoneNumber\",\n  \"sourceId\": \"string\"\n}")
  .asString();
```

```php
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api.smallest.ai/atoms/v1/agent/agentId/caller-ids', [
  'body' => '{
  "sourceKind": "phoneNumber",
  "sourceId": "string"
}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

echo $response->getBody();
```

```csharp
using RestSharp;

var client = new RestClient("https://api.smallest.ai/atoms/v1/agent/agentId/caller-ids");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"sourceKind\": \"phoneNumber\",\n  \"sourceId\": \"string\"\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = [
  "sourceKind": "phoneNumber",
  "sourceId": "string"
] as [String : Any]

let postData = JSONSerialization.data(withJSONObject: parameters, options: [])

let request = NSMutableURLRequest(url: NSURL(string: "https://api.smallest.ai/atoms/v1/agent/agentId/caller-ids")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers
request.httpBody = postData as Data

let session = URLSession.shared
let dataTask = session.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
  if (error != nil) {
    print(error as Any)
  } else {
    let httpResponse = response as? HTTPURLResponse
    print(httpResponse)
  }
})

dataTask.resume()
```