Telnyx Voice Gather - JavaScript

Installation

npm install telnyx

Setup

import Telnyx from 'telnyx';

const client = new Telnyx({
  apiKey: process.env['TELNYX_API_KEY'], // This is the default and can be omitted
});

All examples below assume client is already initialized as shown above.

Error Handling

All API calls can fail with network errors, rate limits (429), validation errors (422), or authentication errors (401). Always handle errors in production code:

try {
  const result = await client.messages.send({ to: '+13125550001', from: '+13125550002', text: 'Hello' });
} catch (err) {
  if (err instanceof Telnyx.APIConnectionError) {
    console.error('Network error — check connectivity and retry');
  } else if (err instanceof Telnyx.RateLimitError) {
    // 429: rate limited — wait and retry with exponential backoff
    const retryAfter = err.headers?.['retry-after'] || 1;
    await new Promise(r => setTimeout(r, retryAfter * 1000));
  } else if (err instanceof Telnyx.APIError) {
    console.error(`API error ${err.status}: ${err.message}`);
    if (err.status === 422) {
      console.error('Validation error — check required fields and formats');
    }
  }
}

Common error codes: 401 invalid API key, 403 insufficient permissions, 404 resource not found, 422 validation error (check field formats), 429 rate limited (retry with exponential backoff).

Add messages to AI Assistant

Add messages to the conversation started by an AI assistant on the call.

POST /calls/{call_control_id}/actions/ai_assistant_add_messages

Optional: client_state (string), command_id (string), messages (array[object])

const response = await client.calls.actions.addAIAssistantMessages('call_control_id');

console.log(response.data);

Returns: result (string)

Start AI Assistant

Start an AI assistant on the call. Expected Webhooks:

• call.conversation.ended
• call.conversation_insights.generated

POST /calls/{call_control_id}/actions/ai_assistant_start

Optional: assistant (object), client_state (string), command_id (string), greeting (string), interruption_settings (object), transcription (object), voice (string), voice_settings (object)

const response = await client.calls.actions.startAIAssistant('call_control_id');

console.log(response.data);

Returns: conversation_id (uuid), result (string)

Stop AI Assistant

Stop an AI assistant on the call.

POST /calls/{call_control_id}/actions/ai_assistant_stop

Optional: client_state (string), command_id (string)

const response = await client.calls.actions.stopAIAssistant('call_control_id');

console.log(response.data);

Returns: result (string)

Gather

Gather DTMF signals to build interactive menus. You can pass a list of valid digits. The Answer command must be issued before the gather command.

POST /calls/{call_control_id}/actions/gather

Optional: client_state (string), command_id (string), gather_id (string), initial_timeout_millis (int32), inter_digit_timeout_millis (int32), maximum_digits (int32), minimum_digits (int32), terminating_digit (string), timeout_millis (int32), valid_digits (string)

const response = await client.calls.actions.gather('call_control_id');

console.log(response.data);

Returns: result (string)

Gather stop

Stop current gather. Expected Webhooks:

• call.gather.ended

POST /calls/{call_control_id}/actions/gather_stop

Optional: client_state (string), command_id (string)

const response = await client.calls.actions.stopGather('call_control_id');

console.log(response.data);

Returns: result (string)

Gather using AI

Gather parameters defined in the request payload using a voice assistant. You can pass parameters described as a JSON Schema object and the voice assistant will attempt to gather these informations.

POST /calls/{call_control_id}/actions/gather_using_ai — Required: parameters

Optional: assistant (object), client_state (string), command_id (string), gather_ended_speech (string), greeting (string), interruption_settings (object), language (object), message_history (array[object]), send_message_history_updates (boolean), send_partial_results (boolean), transcription (object), user_response_timeout_ms (integer), voice (string), voice_settings (object)

const response = await client.calls.actions.gatherUsingAI('call_control_id', {
  parameters: {
    properties: 'bar',
    required: 'bar',
    type: 'bar',
  },
});

console.log(response.data);

Returns: conversation_id (uuid), result (string)

Gather using audio

Play an audio file on the call until the required DTMF signals are gathered to build interactive menus. You can pass a list of valid digits along with an 'invalid_audio_url', which will be played back at the beginning of each prompt. Playback will be interrupted when a DTMF signal is received.

POST /calls/{call_control_id}/actions/gather_using_audio

Optional: audio_url (string), client_state (string), command_id (string), inter_digit_timeout_millis (int32), invalid_audio_url (string), invalid_media_name (string), maximum_digits (int32), maximum_tries (int32), media_name (string), minimum_digits (int32), terminating_digit (string), timeout_millis (int32), valid_digits (string)

const response = await client.calls.actions.gatherUsingAudio('call_control_id');

console.log(response.data);

Returns: result (string)

Gather using speak

Convert text to speech and play it on the call until the required DTMF signals are gathered to build interactive menus. You can pass a list of valid digits along with an 'invalid_payload', which will be played back at the beginning of each prompt. Speech will be interrupted when a DTMF signal is received.

POST /calls/{call_control_id}/actions/gather_using_speak — Required: voice, payload

Optional: client_state (string), command_id (string), inter_digit_timeout_millis (int32), invalid_payload (string), language (enum: arb, cmn-CN, cy-GB, da-DK, de-DE, en-AU, en-GB, en-GB-WLS, en-IN, en-US, es-ES, es-MX, es-US, fr-CA, fr-FR, hi-IN, is-IS, it-IT, ja-JP, ko-KR, nb-NO, nl-NL, pl-PL, pt-BR, pt-PT, ro-RO, ru-RU, sv-SE, tr-TR), maximum_digits (int32), maximum_tries (int32), minimum_digits (int32), payload_type (enum: text, ssml), service_level (enum: basic, premium), terminating_digit (string), timeout_millis (int32), valid_digits (string), voice_settings (object)

const response = await client.calls.actions.gatherUsingSpeak('call_control_id', {
  payload: 'say this on call',
  voice: 'male',
});

console.log(response.data);

Returns: result (string)

---

Webhooks

Webhook Verification

Telnyx signs webhooks with Ed25519. Each request includes telnyx-signature-ed25519 and telnyx-timestamp headers. Always verify signatures in production:

// In your webhook handler (e.g., Express — use raw body, not parsed JSON):
app.post('/webhooks', express.raw({ type: 'application/json' }), async (req, res) => {
  try {
    const event = await client.webhooks.unwrap(req.body.toString(), {
      headers: req.headers,
    });
    // Signature valid — event is the parsed webhook payload
    console.log('Received event:', event.data.event_type);
    res.status(200).send('OK');
  } catch (err) {
    console.error('Webhook verification failed:', err.message);
    res.status(400).send('Invalid signature');
  }
});

The following webhook events are sent to your configured webhook URL. All webhooks include telnyx-timestamp and telnyx-signature-ed25519 headers for Ed25519 signature verification. Use client.webhooks.unwrap() to verify.

Event	Description
CallAIGatherEnded	Call AI Gather Ended
CallAIGatherMessageHistoryUpdated	Call AI Gather Message History Updated
CallAIGatherPartialResults	Call AI Gather Partial Results
callGatherEnded	Call Gather Ended

Webhook payload fields

CallAIGatherEnded

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.ai_gather.ended	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Telnyx connection ID used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.message_history	array[object]	The history of the messages exchanged during the AI gather
data.payload.result	object	The result of the AI gather, its type depends of the parameters provided in the command
data.payload.status	enum: valid, invalid	Reflects how command ended.

CallAIGatherMessageHistoryUpdated

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.ai_gather.message_history_updated	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Telnyx connection ID used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.message_history	array[object]	The history of the messages exchanged during the AI gather

CallAIGatherPartialResults

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.ai_gather.partial_results	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Telnyx connection ID used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.message_history	array[object]	The history of the messages exchanged during the AI gather
data.payload.partial_results	object	The partial result of the AI gather, its type depends of the parameters provided in the command

callGatherEnded

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.gather.ended	The type of event being delivered.
data.id	uuid	Identifies the type of resource.
data.occurred_at	date-time	ISO 8601 datetime of when the event occurred.
data.payload.call_control_id	string	Call ID used to issue commands via Call Control API.
data.payload.connection_id	string	Call Control App ID (formerly Telnyx connection ID) used in the call.
data.payload.call_leg_id	string	ID that is unique to the call and can be used to correlate webhook events.
data.payload.call_session_id	string	ID that is unique to the call session and can be used to correlate webhook events.
data.payload.client_state	string	State received from a command.
data.payload.from	string	Number or SIP URI placing the call.
data.payload.to	string	Destination number or SIP URI of the call.
data.payload.digits	string	The received DTMF digit or symbol.
data.payload.status	enum: valid, invalid, call_hangup, cancelled, cancelled_amd, timeout	Reflects how command ended.