Telnyx Voice Advanced Curl

Telnyx Voice Advanced - curl

Installation

# curl is pre-installed on macOS, Linux, and Windows 10+

Setup

export TELNYX_API_KEY="YOUR_API_KEY_HERE"

All examples below use $TELNYX_API_KEY for authentication.

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:

# Check HTTP status code in response
response=$(curl -s -w "\n%{http_code}" \
  -X POST "https://api.telnyx.com/v2/messages" \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"to": "+13125550001", "from": "+13125550002", "text": "Hello"}')

http_code=$(echo "$response" | tail -1)
body=$(echo "$response" | sed '$d')

case $http_code in
  2*) echo "Success: $body" ;;
  422) echo "Validation error — check required fields and formats" ;;
  429) echo "Rate limited — retry after delay"; sleep 1 ;;
  401) echo "Authentication failed — check TELNYX_API_KEY" ;;
  *)   echo "Error $http_code: $body" ;;
esac

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).

Join AI Assistant Conversation

Add a participant to an existing AI assistant conversation. Use this command to bring an additional call leg into a running AI conversation.

POST /calls/{call_control_id}/actions/ai_assistant_join — Required: conversation_id, participant

Optional: client_state (string), command_id (string)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "conversation_id": "v3:abc123",
  "participant": {}
}' \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/ai_assistant_join"

Returns: conversation_id (uuid), result (string)

Update client state

Updates client state

PUT /calls/{call_control_id}/actions/client_state_update — Required: client_state

curl \
  -X PUT \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "client_state": "aGF2ZSBhIG5pY2UgZGF5ID1d"
}' \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/client_state_update"

Returns: result (string)

Start Conversation Relay

Start a Conversation Relay session on an active call. Conversation Relay connects the call audio to your WebSocket so your application can exchange realtime messages with the caller while Telnyx handles speech recognition and text-to-speech. Only one AI Assistant or Conversation Relay session can be active on a call at a time.

POST /calls/{call_control_id}/actions/conversation_relay_start

Optional: assistant (object), client_state (string), command_id (string), conversation_relay_dtmf_detection (boolean), conversation_relay_settings (object), conversation_relay_url (string), custom_parameters (object), dtmf_detection (boolean), greeting (string), interruptible (enum: none, any, speech, dtmf), interruptible_greeting (enum: none, any, speech, dtmf), interruption_settings (object), language (string), languages (array[object]), provider (string), structured_provider (object), transcription (object), transcription_engine (enum: Google, Telnyx, Deepgram, Azure, xAI, AssemblyAI, Speechmatics, Soniox, A, B), transcription_engine_config (object), tts_provider (string), url (string), voice (string), voice_settings (object)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/conversation_relay_start"

Returns: conversation_relay_id (string), result (string)

Stop Conversation Relay

Stop the active Conversation Relay session on a call.

POST /calls/{call_control_id}/actions/conversation_relay_stop

Optional: client_state (string), command_id (string)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/conversation_relay_stop"

Returns: result (string)

Send DTMF

Sends DTMF tones from this leg. DTMF tones will be heard by the other end of the call. Expected Webhooks:

There are no webhooks associated with this command.

POST /calls/{call_control_id}/actions/send_dtmf — Required: digits

Optional: client_state (string), command_id (string), duration_millis (int32)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "digits": "1www2WABCDw9"
}' \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/send_dtmf"

Returns: result (string)

SIPREC start

Start siprec session to configured in SIPREC connector SRS.

Expected Webhooks:

• siprec.started
• siprec.stopped
• siprec.failed

POST /calls/{call_control_id}/actions/siprec_start

Optional: client_state (string), connector_name (string), include_metadata_custom_headers (boolean), secure (boolean), session_timeout_secs (integer), sip_transport (enum: udp, tcp, tls), siprec_track (enum: inbound_track, outbound_track, both_tracks)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/siprec_start"

Returns: result (string)

SIPREC stop

Stop SIPREC session. Expected Webhooks:

• siprec.stopped

POST /calls/{call_control_id}/actions/siprec_stop

Optional: client_state (string), command_id (string)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/siprec_stop"

Returns: result (string)

Noise Suppression Start (BETA)

POST /calls/{call_control_id}/actions/suppression_start

Optional: client_state (string), command_id (string), direction (enum: inbound, outbound, both), noise_suppression_engine (enum: Denoiser, DeepFilterNet, Krisp, AiCoustics, aic_l_quail, aic_l_rook, aic_s_quail, aic_s_rook, quail_voice_focus_s, quail_voice_focus_xs), noise_suppression_engine_config (object)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/suppression_start"

Returns: result (string)

Noise Suppression Stop (BETA)

POST /calls/{call_control_id}/actions/suppression_stop

Optional: client_state (string), command_id (string)

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/suppression_stop"

Returns: result (string)

Switch supervisor role

Switch the supervisor role for a bridged call. This allows switching between different supervisor modes during an active call

POST /calls/{call_control_id}/actions/switch_supervisor_role — Required: role

curl \
  -X POST \
  -H "Authorization: Bearer $TELNYX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "role": "barge"
}' \
  "https://api.telnyx.com/v2/calls/v3:550e8400-e29b-41d4-a716-446655440000_gRU1OGRkYQ/actions/switch_supervisor_role"

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:

# Telnyx signs webhooks with Ed25519 (asymmetric — NOT HMAC/Standard Webhooks).
# Headers sent with each webhook:
#   telnyx-signature-ed25519: base64-encoded Ed25519 signature
#   telnyx-timestamp: Unix timestamp (reject if >5 minutes old for replay protection)
#
# Get your public key from: Telnyx Portal > Account Settings > Keys & Credentials
# Use the Telnyx SDK in your language for verification (client.webhooks.unwrap).
# Your endpoint MUST return 2xx within 2 seconds or Telnyx will retry (up to 3 attempts).
# Configure a failover URL in Telnyx Portal for additional reliability.

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.

Webhook payload fields

callConversationEnded

callConversationInsightsGenerated

callDtmfReceived

callMachineDetectionEnded

callMachineGreetingEnded

callMachinePremiumDetectionEnded

callMachinePremiumGreetingEnded

callReferCompleted

callReferFailed

callReferStarted

callSiprecFailed

callSiprecStarted

callSiprecStopped