Call conversation start failed
Emitted when an AI assistant requested with an answer command (assistant.id) could not be started after the call was answered, for example because the assistant ID does not exist. No conversation is created, so neither call.conversation.created nor call.conversation.ended is sent for this attempt. The call stays answered: use this event to continue the call, for example by transferring it, playing a message, or hanging up. data.payload.reason is invalid_request when the request was rejected and service_error otherwise.
This webhook uses Telnyx headers (telnyx-timestamp, telnyx-signature-ed25519) that are compatible with Standard Webhooks specification for SDK generation. Custom validation logic can map these to standard webhook-timestamp and webhook-signature equivalents. See https://github.com/standard-webhooks/standard-webhooks for details.
{
"data": {
"record_type": "event",
"event_type": "call.conversation.start_failed",
"id": "3f1c2a9e-8d4b-4c6e-9a7f-1b2c3d4e5f60",
"occurred_at": "2025-05-29T13:35:38.817785Z",
"created_at": "2025-05-29T13:35:38.927621Z",
"payload": {
"assistant_id": "assistant-d9082b56-ba2d-4ad1-a50c-58661eb1463d",
"call_control_id": "v3:HDR1vQHx697hpP9xZ0bhlbUOWPFPDtPcxw-nuSMuC6mGVpb0euoklQ",
"call_leg_id": "cc29cce6-3c91-11f0-a8e5-02420aef3d20",
"call_session_id": "cc29c8d6-3c91-11f0-aa7c-02420aef3d20",
"client_state": "g3QAAAACbQAAAAtkYXRhX2NlbnRlcm0AAAADY2gxbQAAAApkZXBsb3ltZW50bQAAAARiYXNl",
"connection_id": "2694492062593582591",
"from": "+13124287921",
"to": "+13125550100",
"reason": "invalid_request"
}
}
}Authorizations
Bearer authentication header of the form Bearer <token>, where <token> is your auth token.
Headers
Unix timestamp (seconds since epoch) of when the webhook was sent - compatible with webhook-timestamp Unix timestamp for replay attack prevention
Base64 encoded Ed25519 signature for webhook verification - compatible with webhook-signature Ed25519 signature of timestamp|payload for verification
Body
The AI assistant requested for the call could not be started, so no conversation was created. No call.conversation.created or call.conversation.ended is sent for this attempt.
Show child attributes
Show child attributes
{
"record_type": "event",
"event_type": "call.conversation.start_failed",
"id": "3f1c2a9e-8d4b-4c6e-9a7f-1b2c3d4e5f60",
"occurred_at": "2025-05-29T13:35:38.817785Z",
"created_at": "2025-05-29T13:35:38.927621Z",
"payload": {
"assistant_id": "assistant-d9082b56-ba2d-4ad1-a50c-58661eb1463d",
"call_control_id": "v3:HDR1vQHx697hpP9xZ0bhlbUOWPFPDtPcxw-nuSMuC6mGVpb0euoklQ",
"call_leg_id": "cc29cce6-3c91-11f0-a8e5-02420aef3d20",
"call_session_id": "cc29c8d6-3c91-11f0-aa7c-02420aef3d20",
"client_state": "g3QAAAACbQAAAAtkYXRhX2NlbnRlcm0AAAADY2gxbQAAAApkZXBsb3ltZW50bQAAAARiYXNl",
"connection_id": "2694492062593582591",
"from": "+13124287921",
"to": "+13125550100",
"reason": "invalid_request"
}
}
Response
The server must return an HTTP 200, otherwise we will reattempt delivery at the failover webhook URL.
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{
"data": {
"record_type": "event",
"event_type": "call.conversation.start_failed",
"id": "3f1c2a9e-8d4b-4c6e-9a7f-1b2c3d4e5f60",
"occurred_at": "2025-05-29T13:35:38.817785Z",
"created_at": "2025-05-29T13:35:38.927621Z",
"payload": {
"assistant_id": "assistant-d9082b56-ba2d-4ad1-a50c-58661eb1463d",
"call_control_id": "v3:HDR1vQHx697hpP9xZ0bhlbUOWPFPDtPcxw-nuSMuC6mGVpb0euoklQ",
"call_leg_id": "cc29cce6-3c91-11f0-a8e5-02420aef3d20",
"call_session_id": "cc29c8d6-3c91-11f0-aa7c-02420aef3d20",
"client_state": "g3QAAAACbQAAAAtkYXRhX2NlbnRlcm0AAAADY2gxbQAAAApkZXBsb3ltZW50bQAAAARiYXNl",
"connection_id": "2694492062593582591",
"from": "+13124287921",
"to": "+13125550100",
"reason": "invalid_request"
}
}
}