> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://developer.jelliu.co/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://developer.jelliu.co/_mcp/server.

# Start a warm transfer

POST https://api.jelliu.co/api/calls/{callId}/transfer
Content-Type: application/json

Moves a live call into a conference and dials `transfer_to`, so a human joins the caller. Finish with `POST /api/calls/{callId}/transfer/complete` (the human keeps the caller) or `POST /api/calls/{callId}/transfer/cancel` (hang up the human and hand the caller back to the AI).

Checks, in order: the destination must pass the workspace's destination policy (premium-rate / toll-fraud prefixes, workspace blocklist, allowed countries; refused with 403 even before the call is looked up, and the refusal is written to the audit log with the masked number); the call must exist; it must have a carrier leg, so calls on a SIP-trunk number cannot be transferred (400); and the carrier must confirm the leg is `in-progress` (400 when not, 409 when the carrier cannot be reached).

**Side effects.** Redirects the caller's leg into a conference (the AI stops speaking at that moment) and places a second, billable outbound call to `transfer_to` from the workspace's own voice number. Stores `transfer_call_sid`, `transferred_at` and `transferred_to` on the call. Writes an audit entry.

**Idempotency.** Not idempotent: each successful request dials `transfer_to` again into a new conference.

**Access**

* **Required scope:** `full`. Signed-in users need the admin or owner role.
* **Rate limit:** Outbound — 20 requests/min per workspace, and also the General API budget (per plan: 120 to 600 requests/min per workspace). See [Rate limits](/rate-limits).
* **Plan:** Available on every plan.

Reference: https://developer.jelliu.co/api-reference/calls/post-calls-by-call-id-transfer

## Authentication

- `Authorization` header (bearer token, required) — Workspace API key: `jl_` followed by 64 lowercase hex characters, created by the workspace owner in the dashboard (**Settings → API Keys**) and sent as `Authorization: Bearer jl_...`. The plaintext is shown once, at creation; Jelliu stores only a SHA-256 hash. A workspace can hold up to 25 active keys. | Scope | GET / HEAD | POST / PUT / PATCH / DELETE | Admin-only routes | | --- | --- | --- | --- | | `read` | Yes | No | No | | `write` | Yes | Yes | No | | `full` | Yes | Yes | Yes | Operations restricted to admins or owners reject keys without the `full` scope with `403`, and say so in their description. No key, whatever its scope, can mint or revoke API keys or rotate a webhook secret — that requires a signed-in owner session. A revoked key stops authenticating within about 10 seconds. See [Authentication](/authentication).

## Request

### Path parameters

- `callId` (string, required) — The live call's id. Must be a UUID (400 `Invalid call ID` otherwise).

### Body (application/json)

This endpoint expects an object.

- `transfer_to` (string, required) — E.164 number of the human to transfer to. Must also be allowed by the workspace's destination policy.

## Response

### 200

The caller is in the conference and the human leg is being dialed.

- `data` (object, required)
  - `transferId` (string, required) — Carrier id of the outbound leg to the human.
  - `conferenceId` (string, required) — Carrier conference id (falls back to the conference's friendly name when the id cannot be resolved yet).

## Errors

### 400 Bad Request Error

Invalid `callId` (`Invalid call ID`) or body (`Invalid transfer input`, `details` = zod `flatten()` output), the call has no carrier leg, or the carrier reports it is not in progress.

- `error` (object, required) — The error object. Always has `code` and `message`.
  - `code` (string, required) — Stable machine-readable error code (for example `VALIDATION_FAILED`, `UNAUTHORIZED`, `FORBIDDEN`, `NOT_FOUND`, `BILLING_ERROR`, `COMPLIANCE_BLOCKED`, `RATE_LIMIT_EXCEEDED`, `INTERNAL_ERROR`). Switch on this, not on `message`. See [Errors](/errors).
  - `message` (string, required) — Human-readable explanation. English or Spanish depending on the route; may change without notice.
  - `details` (object or list of object, optional) — Present on `VALIDATION_FAILED` only. Its shape depends on how the route validates: * a field map, either Zod's `flatten()` output (`{ "formErrors": [], "fieldErrors": { "name": ["..."] } }`) or just its `fieldErrors` part (`{ "name": ["..."] }`); * an issue list, where each issue has at least `path`, `message` and `code`. `path` is a dot-separated string on routes that let the schema throw, and an array of keys on routes that forward Zod's raw issues (those also carry Zod's extra issue fields).
    - Field map
      - `formErrors` (list of string, optional)
      - `fieldErrors` (map from string to list of string, optional)
  - `metadata` (map from string to any, optional) — Structured detail exposed for a small allowlist of codes only — for example `BILLING_ERROR` carries `limit`, `current` and `tier` (resource caps) or `tier` and `feature` (feature gates).

### 401 Unauthorized Error

No usable credential. Either the `Authorization` header is missing or is not a well-formed `Bearer jl_…` key, or the key is unknown, revoked or expired. Do not retry with the same key. See [Authentication](/authentication#401-unauthorized).

- `error` (object, required) — The error object. Always has `code` and `message`.
  - `code` (string, required) — Stable machine-readable error code (for example `VALIDATION_FAILED`, `UNAUTHORIZED`, `FORBIDDEN`, `NOT_FOUND`, `BILLING_ERROR`, `COMPLIANCE_BLOCKED`, `RATE_LIMIT_EXCEEDED`, `INTERNAL_ERROR`). Switch on this, not on `message`. See [Errors](/errors).
  - `message` (string, required) — Human-readable explanation. English or Spanish depending on the route; may change without notice.
  - `details` (object or list of object, optional) — Present on `VALIDATION_FAILED` only. Its shape depends on how the route validates: * a field map, either Zod's `flatten()` output (`{ "formErrors": [], "fieldErrors": { "name": ["..."] } }`) or just its `fieldErrors` part (`{ "name": ["..."] }`); * an issue list, where each issue has at least `path`, `message` and `code`. `path` is a dot-separated string on routes that let the schema throw, and an array of keys on routes that forward Zod's raw issues (those also carry Zod's extra issue fields).
    - Field map
      - `formErrors` (list of string, optional)
      - `fieldErrors` (map from string to list of string, optional)
  - `metadata` (map from string to any, optional) — Structured detail exposed for a small allowlist of codes only — for example `BILLING_ERROR` carries `limit`, `current` and `tier` (resource caps) or `tier` and `feature` (feature gates).

### 403 Forbidden Error

The destination is refused by the destination policy (`COMPLIANCE_BLOCKED`), the API key lacks the `full` scope, or the signed-in user is not an admin or owner.

- `error` (object, required) — The error object. Always has `code` and `message`.
  - `code` (string, required) — Stable machine-readable error code (for example `VALIDATION_FAILED`, `UNAUTHORIZED`, `FORBIDDEN`, `NOT_FOUND`, `BILLING_ERROR`, `COMPLIANCE_BLOCKED`, `RATE_LIMIT_EXCEEDED`, `INTERNAL_ERROR`). Switch on this, not on `message`. See [Errors](/errors).
  - `message` (string, required) — Human-readable explanation. English or Spanish depending on the route; may change without notice.
  - `details` (object or list of object, optional) — Present on `VALIDATION_FAILED` only. Its shape depends on how the route validates: * a field map, either Zod's `flatten()` output (`{ "formErrors": [], "fieldErrors": { "name": ["..."] } }`) or just its `fieldErrors` part (`{ "name": ["..."] }`); * an issue list, where each issue has at least `path`, `message` and `code`. `path` is a dot-separated string on routes that let the schema throw, and an array of keys on routes that forward Zod's raw issues (those also carry Zod's extra issue fields).
    - Field map
      - `formErrors` (list of string, optional)
      - `fieldErrors` (map from string to list of string, optional)
  - `metadata` (map from string to any, optional) — Structured detail exposed for a small allowlist of codes only — for example `BILLING_ERROR` carries `limit`, `current` and `tier` (resource caps) or `tier` and `feature` (feature gates).

### 404 Not Found Error

The call does not exist, was deleted, or belongs to another workspace.

- `error` (object, required) — The error object. Always has `code` and `message`.
  - `code` (string, required) — Stable machine-readable error code (for example `VALIDATION_FAILED`, `UNAUTHORIZED`, `FORBIDDEN`, `NOT_FOUND`, `BILLING_ERROR`, `COMPLIANCE_BLOCKED`, `RATE_LIMIT_EXCEEDED`, `INTERNAL_ERROR`). Switch on this, not on `message`. See [Errors](/errors).
  - `message` (string, required) — Human-readable explanation. English or Spanish depending on the route; may change without notice.
  - `details` (object or list of object, optional) — Present on `VALIDATION_FAILED` only. Its shape depends on how the route validates: * a field map, either Zod's `flatten()` output (`{ "formErrors": [], "fieldErrors": { "name": ["..."] } }`) or just its `fieldErrors` part (`{ "name": ["..."] }`); * an issue list, where each issue has at least `path`, `message` and `code`. `path` is a dot-separated string on routes that let the schema throw, and an array of keys on routes that forward Zod's raw issues (those also carry Zod's extra issue fields).
    - Field map
      - `formErrors` (list of string, optional)
      - `fieldErrors` (map from string to list of string, optional)
  - `metadata` (map from string to any, optional) — Structured detail exposed for a small allowlist of codes only — for example `BILLING_ERROR` carries `limit`, `current` and `tier` (resource caps) or `tier` and `feature` (feature gates).

### 409 Conflict Error

The carrier's live state of the call could not be confirmed; retry shortly.

- `error` (object, required) — The error object. Always has `code` and `message`.
  - `code` (string, required) — Stable machine-readable error code (for example `VALIDATION_FAILED`, `UNAUTHORIZED`, `FORBIDDEN`, `NOT_FOUND`, `BILLING_ERROR`, `COMPLIANCE_BLOCKED`, `RATE_LIMIT_EXCEEDED`, `INTERNAL_ERROR`). Switch on this, not on `message`. See [Errors](/errors).
  - `message` (string, required) — Human-readable explanation. English or Spanish depending on the route; may change without notice.
  - `details` (object or list of object, optional) — Present on `VALIDATION_FAILED` only. Its shape depends on how the route validates: * a field map, either Zod's `flatten()` output (`{ "formErrors": [], "fieldErrors": { "name": ["..."] } }`) or just its `fieldErrors` part (`{ "name": ["..."] }`); * an issue list, where each issue has at least `path`, `message` and `code`. `path` is a dot-separated string on routes that let the schema throw, and an array of keys on routes that forward Zod's raw issues (those also carry Zod's extra issue fields).
    - Field map
      - `formErrors` (list of string, optional)
      - `fieldErrors` (map from string to list of string, optional)
  - `metadata` (map from string to any, optional) — Structured detail exposed for a small allowlist of codes only — for example `BILLING_ERROR` carries `limit`, `current` and `tier` (resource caps) or `tier` and `feature` (feature gates).

### 429 Too Many Requests Error

The outbound budget (20 requests/min) or the general budget is spent.

- `error` (object, required) — The error object. Always has `code` and `message`.
  - `code` (string, required) — Stable machine-readable error code (for example `VALIDATION_FAILED`, `UNAUTHORIZED`, `FORBIDDEN`, `NOT_FOUND`, `BILLING_ERROR`, `COMPLIANCE_BLOCKED`, `RATE_LIMIT_EXCEEDED`, `INTERNAL_ERROR`). Switch on this, not on `message`. See [Errors](/errors).
  - `message` (string, required) — Human-readable explanation. English or Spanish depending on the route; may change without notice.
  - `details` (object or list of object, optional) — Present on `VALIDATION_FAILED` only. Its shape depends on how the route validates: * a field map, either Zod's `flatten()` output (`{ "formErrors": [], "fieldErrors": { "name": ["..."] } }`) or just its `fieldErrors` part (`{ "name": ["..."] }`); * an issue list, where each issue has at least `path`, `message` and `code`. `path` is a dot-separated string on routes that let the schema throw, and an array of keys on routes that forward Zod's raw issues (those also carry Zod's extra issue fields).
    - Field map
      - `formErrors` (list of string, optional)
      - `fieldErrors` (map from string to list of string, optional)
  - `metadata` (map from string to any, optional) — Structured detail exposed for a small allowlist of codes only — for example `BILLING_ERROR` carries `limit`, `current` and `tier` (resource caps) or `tier` and `feature` (feature gates).

### 502 Bad Gateway Error

The carrier rejected the redirect or the dial (`TELEPHONY_ERROR`; message replaced by `Internal server error`). The caller may already have been moved into the conference.

- `error` (object, required) — The error object. Always has `code` and `message`.
  - `code` (string, required) — Stable machine-readable error code (for example `VALIDATION_FAILED`, `UNAUTHORIZED`, `FORBIDDEN`, `NOT_FOUND`, `BILLING_ERROR`, `COMPLIANCE_BLOCKED`, `RATE_LIMIT_EXCEEDED`, `INTERNAL_ERROR`). Switch on this, not on `message`. See [Errors](/errors).
  - `message` (string, required) — Human-readable explanation. English or Spanish depending on the route; may change without notice.
  - `details` (object or list of object, optional) — Present on `VALIDATION_FAILED` only. Its shape depends on how the route validates: * a field map, either Zod's `flatten()` output (`{ "formErrors": [], "fieldErrors": { "name": ["..."] } }`) or just its `fieldErrors` part (`{ "name": ["..."] }`); * an issue list, where each issue has at least `path`, `message` and `code`. `path` is a dot-separated string on routes that let the schema throw, and an array of keys on routes that forward Zod's raw issues (those also carry Zod's extra issue fields).
    - Field map
      - `formErrors` (list of string, optional)
      - `fieldErrors` (map from string to list of string, optional)
  - `metadata` (map from string to any, optional) — Structured detail exposed for a small allowlist of codes only — for example `BILLING_ERROR` carries `limit`, `current` and `tier` (resource caps) or `tier` and `feature` (feature gates).

## Examples

### Calls_postCallsByCallIdTransfer_example

**Request**

```json
undefined
```

**Response**

```json
{
  "data": {
    "transferId": "CA3f1e2d4c5b6a7980f1e2d3c4b5a69788",
    "conferenceId": "CF9a8b7c6d5e4f30211a2b3c4d5e6f7a8b"
  }
}
```

**SDK Code**

```python Calls_postCallsByCallIdTransfer_example
import requests

url = "https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer"

headers = {"Authorization": "Bearer <token>"}

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

print(response.json())
```

```javascript Calls_postCallsByCallIdTransfer_example
const url = 'https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer';
const options = {method: 'POST', headers: {Authorization: 'Bearer <token>'}};

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

```go Calls_postCallsByCallIdTransfer_example
package main

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

func main() {

	url := "https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer"

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

	req.Header.Add("Authorization", "Bearer <token>")

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

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

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

}
```

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

url = URI("https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'

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

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

HttpResponse<String> response = Unirest.post("https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer")
  .header("Authorization", "Bearer <token>")
  .asString();
```

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

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer', [
  'headers' => [
    'Authorization' => 'Bearer <token>',
  ],
]);

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

```csharp Calls_postCallsByCallIdTransfer_example
using RestSharp;

var client = new RestClient("https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
IRestResponse response = client.Execute(request);
```

```swift Calls_postCallsByCallIdTransfer_example
import Foundation

let headers = ["Authorization": "Bearer <token>"]

let request = NSMutableURLRequest(url: NSURL(string: "https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer")! as URL,
                                        cachePolicy: .useProtocolCachePolicy,
                                    timeoutInterval: 10.0)
request.httpMethod = "POST"
request.allHTTPHeaderFields = headers

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()
```

### Transfer to a supervisor's mobile

**Request**

```json
{
  "transfer_to": "+573109876543"
}
```

**Response**

```json
{
  "data": {
    "transferId": "CA3f1e2d4c5b6a7980f1e2d3c4b5a69788",
    "conferenceId": "CF9a8b7c6d5e4f30211a2b3c4d5e6f7a8b"
  }
}
```

**SDK Code**

```python Transfer to a supervisor's mobile
import requests

url = "https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer"

payload = { "transfer_to": "+573109876543" }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.json())
```

```javascript Transfer to a supervisor's mobile
const url = 'https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer';
const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: '{"transfer_to":"+573109876543"}'
};

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

```go Transfer to a supervisor's mobile
package main

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

func main() {

	url := "https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer"

	payload := strings.NewReader("{\n  \"transfer_to\": \"+573109876543\"\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 Transfer to a supervisor's mobile
require 'uri'
require 'net/http'

url = URI("https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer")

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  \"transfer_to\": \"+573109876543\"\n}"

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

```java Transfer to a supervisor's mobile
import com.mashape.unirest.http.HttpResponse;
import com.mashape.unirest.http.Unirest;

HttpResponse<String> response = Unirest.post("https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"transfer_to\": \"+573109876543\"\n}")
  .asString();
```

```php Transfer to a supervisor's mobile
<?php
require_once('vendor/autoload.php');

$client = new \GuzzleHttp\Client();

$response = $client->request('POST', 'https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer', [
  'body' => '{
  "transfer_to": "+573109876543"
}',
  'headers' => [
    'Authorization' => 'Bearer <token>',
    'Content-Type' => 'application/json',
  ],
]);

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

```csharp Transfer to a supervisor's mobile
using RestSharp;

var client = new RestClient("https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer");
var request = new RestRequest(Method.POST);
request.AddHeader("Authorization", "Bearer <token>");
request.AddHeader("Content-Type", "application/json");
request.AddParameter("application/json", "{\n  \"transfer_to\": \"+573109876543\"\n}", ParameterType.RequestBody);
IRestResponse response = client.Execute(request);
```

```swift Transfer to a supervisor's mobile
import Foundation

let headers = [
  "Authorization": "Bearer <token>",
  "Content-Type": "application/json"
]
let parameters = ["transfer_to": "+573109876543"] as [String : Any]

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

let request = NSMutableURLRequest(url: NSURL(string: "https://api.jelliu.co/api/calls/8d0f3c1e-5b7a-4c52-9d0e-2a6f1b3c4d5e/transfer")! 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()
```