Telnyx Voice - Python

Installation

pip install telnyx

Setup

import os
from telnyx import Telnyx

client = Telnyx(
    api_key=os.environ.get("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:

import telnyx

try:
    response = client.calls.dial(
        connection_id="7267xxxxxxxxxxxxxx",
        from_="+18005550101",
        to="+18005550100",
    )
except telnyx.APIConnectionError:
    print("Network error — check connectivity and retry")
except telnyx.RateLimitError:
    import time
    time.sleep(1)  # Check Retry-After header for actual delay
except telnyx.APIStatusError as e:
    print(f"API error {e.status_code}: {e.message}")
    if e.status_code == 422:
        print("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).

Important Notes

• Phone numbers must be in E.164 format (e.g., +13125550001). Include the + prefix and country code. No spaces, dashes, or parentheses.
• Pagination: List methods return an auto-paginating iterator. Use for item in page_result: to iterate through all pages automatically.

Operational Caveats

• Call Control is event-driven. After dial() or an inbound webhook, issue follow-up commands from webhook handlers using the call_control_id in the event payload.
• Outbound and inbound flows are different: outbound calls start with dial(), while inbound calls must be answered from the incoming webhook before other commands run.
• A publicly reachable webhook endpoint is required for real call control. Without it, calls may connect but your application cannot drive the live call state.

Reference Use Rules

Do not invent Telnyx parameters, enums, response fields, or webhook fields.

• If the parameter, enum, or response field you need is not shown inline in this skill, read references/api-details.md before writing code.
• Before using any operation in ## Additional Operations, read the optional-parameters section and the response-schemas section.
• Before reading or matching webhook fields beyond the inline examples, read the webhook payload reference.

Core Tasks

Dial an outbound call

Primary voice entrypoint. Agents need the async call-control identifiers returned here.

client.calls.dial() — POST /calls

Parameter	Type	Required	Description
to	string (E.164)	Yes	The DID or SIP URI to dial out to.
from_	string (E.164)	Yes	The from number to be used as the caller id presented to t...
connection_id	string (UUID)	Yes	The ID of the Call Control App (formerly ID of the connectio...
timeout_secs	integer	No	The number of seconds that Telnyx will wait for the call to ...
billing_group_id	string (UUID)	No	Use this field to set the Billing Group ID for the call.
client_state	string	No	Use this field to add state to every subsequent webhook.
...			+48 optional params in references/api-details.md

response = client.calls.dial(
    connection_id="7267xxxxxxxxxxxxxx",
    from_="+18005550101",
    to="+18005550100",
)
print(response.data)

Primary response fields:

• response.data.call_control_id
• response.data.call_leg_id
• response.data.call_session_id
• response.data.is_alive
• response.data.recording_id
• response.data.call_duration

Answer an inbound call

Primary inbound call-control command.

client.calls.actions.answer() — POST /calls/{call_control_id}/actions/answer

Parameter	Type	Required	Description
call_control_id	string (UUID)	Yes	Unique identifier and token for controlling the call
billing_group_id	string (UUID)	No	Use this field to set the Billing Group ID for the call.
client_state	string	No	Use this field to add state to every subsequent webhook.
webhook_url	string (URL)	No	Use this field to override the URL for which Telnyx will sen...
...			+26 optional params in references/api-details.md

response = client.calls.actions.answer(
    call_control_id="550e8400-e29b-41d4-a716-446655440000",
)
print(response.data)

Primary response fields:

• response.data.result
• response.data.recording_id

Transfer a live call

Common post-answer control path with downstream webhook implications.

client.calls.actions.transfer() — POST /calls/{call_control_id}/actions/transfer

Parameter	Type	Required	Description
to	string (E.164)	Yes	The DID or SIP URI to dial out to.
call_control_id	string (UUID)	Yes	Unique identifier and token for controlling the call
timeout_secs	integer	No	The number of seconds that Telnyx will wait for the call to ...
client_state	string	No	Use this field to add state to every subsequent webhook.
webhook_url	string (URL)	No	Use this field to override the URL for which Telnyx will sen...
...			+33 optional params in references/api-details.md

response = client.calls.actions.transfer(
    call_control_id="550e8400-e29b-41d4-a716-446655440000",
    to="+18005550100",
)
print(response.data)

Primary response fields:

• response.data.result

---

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., Flask — use raw body, not parsed JSON):
@app.route("/webhooks", methods=["POST"])
def handle_webhook():
    payload = request.get_data(as_text=True)  # raw body as string
    headers = dict(request.headers)
    try:
        event = client.webhooks.unwrap(payload, headers=headers)
    except Exception as e:
        print(f"Webhook verification failed: {e}")
        return "Invalid signature", 400
    # Signature valid — event is the parsed webhook payload
    print(f"Received event: {event.data.event_type}")
    return "OK", 200

Webhooks

These webhook payload fields are inline because they are part of the primary integration path.

Call Answered

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.answered	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 ev...

Call Hangup

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.hangup	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 ev...

Call Initiated

Field	Type	Description
data.record_type	enum: event	Identifies the type of the resource.
data.event_type	enum: call.initiated	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.connection_codecs	string	The list of comma-separated codecs enabled for the connection.
data.payload.offered_codecs	string	The list of comma-separated codecs offered by caller.

If you need webhook fields that are not listed inline here, read the webhook payload reference before writing the handler.

---

Important Supporting Operations

Use these when the core tasks above are close to your flow, but you need a common variation or follow-up step.

Hangup call

End a live call from your webhook-driven control flow.

client.calls.actions.hangup() — POST /calls/{call_control_id}/actions/hangup

Parameter	Type	Required	Description
call_control_id	string (UUID)	Yes	Unique identifier and token for controlling the call
client_state	string	No	Use this field to add state to every subsequent webhook.
command_id	string (UUID)	No	Use this field to avoid duplicate commands.
custom_headers	array[object]	No	Custom headers to be added to the SIP BYE message.

response = client.calls.actions.hangup(
    call_control_id="550e8400-e29b-41d4-a716-446655440000",
)
print(response.data)

Primary response fields:

• response.data.result

Bridge calls

Trigger a follow-up action in an existing workflow rather than creating a new top-level resource.

client.calls.actions.bridge() — POST /calls/{call_control_id}/actions/bridge

Parameter	Type	Required	Description
call_control_id	string (UUID)	Yes	The Call Control ID of the call you want to bridge with, can...
call_control_id	string (UUID)	Yes	Unique identifier and token for controlling the call
client_state	string	No	Use this field to add state to every subsequent webhook.
command_id	string (UUID)	No	Use this field to avoid duplicate commands.
video_room_id	string (UUID)	No	The ID of the video room you want to bridge with, can't be u...
...			+16 optional params in references/api-details.md

response = client.calls.actions.bridge(
    call_control_id_to_bridge="call_control_id",
    call_control_id_to_bridge_with="v3:MdI91X4lWFEs7IgbBEOT9M4AigoY08M0WWZFISt1Yw2axZ_IiE4pqg",
)
print(response.data)

Primary response fields:

• response.data.result

Reject a call

Trigger a follow-up action in an existing workflow rather than creating a new top-level resource.

client.calls.actions.reject() — POST /calls/{call_control_id}/actions/reject

Parameter	Type	Required	Description
cause	enum (CALL_REJECTED, USER_BUSY)	Yes	Cause for call rejection.
call_control_id	string (UUID)	Yes	Unique identifier and token for controlling the call
client_state	string	No	Use this field to add state to every subsequent webhook.
command_id	string (UUID)	No	Use this field to avoid duplicate commands.

response = client.calls.actions.reject(
    call_control_id="550e8400-e29b-41d4-a716-446655440000",
    cause="USER_BUSY",
)
print(response.data)

Primary response fields:

• response.data.result

Retrieve a call status

Fetch the current state before updating, deleting, or making control-flow decisions.

client.calls.retrieve_status() — GET /calls/{call_control_id}

Parameter	Type	Required	Description
call_control_id	string (UUID)	Yes	Unique identifier and token for controlling the call

response = client.calls.retrieve_status(
    "call_control_id",
)
print(response.data)

Primary response fields:

• response.data.call_control_id
• response.data.call_duration
• response.data.call_leg_id
• response.data.call_session_id
• response.data.client_state
• response.data.end_time

List all active calls for given connection

Fetch the current state before updating, deleting, or making control-flow decisions.

client.connections.list_active_calls() — GET /connections/{connection_id}/active_calls

Parameter	Type	Required	Description
connection_id	string (UUID)	Yes	Telnyx connection id
page	object	No	Consolidated page parameter (deepObject style).

page = client.connections.list_active_calls(
    connection_id="1293384261075731461",
)
page = page.data[0]
print(page.call_control_id)

Response wrapper:

• items: page.data
• pagination: page.meta

Primary item fields:

• call_control_id
• call_duration
• call_leg_id
• call_session_id
• client_state
• record_type

List call control applications

Inspect available resources or choose an existing resource before mutating it.

client.call_control_applications.list() — GET /call_control_applications

Parameter	Type	Required	Description
sort	enum (created_at, connection_name, active)	No	Specifies the sort order for results.
filter	object	No	Consolidated filter parameter (deepObject style).
page	object	No	Consolidated page parameter (deepObject style).

page = client.call_control_applications.list()
page = page.data[0]
print(page.id)

Response wrapper:

• items: page.data
• pagination: page.meta

Primary item fields:

• id
• created_at
• updated_at
• active
• anchorsite_override
• application_name

---

Additional Operations

Use the core tasks above first. The operations below are indexed here with exact SDK methods and required params; use references/api-details.md for full optional params, response schemas, and lower-frequency webhook payloads. Before using any operation below, read the optional-parameters section and the response-schemas section so you do not guess missing fields.

Operation	SDK method	Endpoint	Use when	Required params
Create a call control application	client.call_control_applications.create()	POST /call_control_applications	Create or provision an additional resource when the core tasks do not cover this flow.	application_name, webhook_event_url
Retrieve a call control application	client.call_control_applications.retrieve()	GET /call_control_applications/{id}	Fetch the current state before updating, deleting, or making control-flow decisions.	id
Update a call control application	client.call_control_applications.update()	PATCH /call_control_applications/{id}	Modify an existing resource without recreating it.	application_name, webhook_event_url, id
Delete a call control application	client.call_control_applications.delete()	DELETE /call_control_applications/{id}	Remove, detach, or clean up an existing resource.	id
SIP Refer a call	client.calls.actions.refer()	POST /calls/{call_control_id}/actions/refer	Trigger a follow-up action in an existing workflow rather than creating a new top-level resource.	sip_address, call_control_id
Send SIP info	client.calls.actions.send_sip_info()	POST /calls/{call_control_id}/actions/send_sip_info	Trigger a follow-up action in an existing workflow rather than creating a new top-level resource.	content_type, body, call_control_id

Other Webhook Events

Event	data.event_type	Description
callBridged	call.bridged	Call Bridged

---

For exhaustive optional parameters, full response schemas, and complete webhook payloads, see references/api-details.md.