----------------------------- **While I generate an answer, here are some sources that might be helpful**: * [Create Phone Call]() * [Call Forwarding]() * [Get Call]() * [List Calls]() -----------------------------

### Answer The issue you're encountering with

unknown-error

following the addition of

forwardedPhoneNumbers

might indeed stem from how the forwarding numbers are handled or set up in your assistant configuration. This error can be linked to various factors, including misconfigurations or unexpected input handling by the assistant. If the configuration of

forwardedPhoneNumbers

or the response format from your server is not correct, it might lead to such errors [(1)]() . To debug this, you can ensure that: 1. The phone numbers in

forwardedPhoneNumbers

are correctly formatted in E.164 format. This is crucial as incorrect number format can cause the API to reject the setup or malfunction [(2)]() . 2. Your server handling the

assistant-request

might need to properly parse and utilize the

forwardedPhoneNumbers

. If the server sends an incorrect response or fails to handle the incoming data correctly, it could result in an

unknown-error

. 3. Check the server logs associated with the call ID

40ad7ba1-8588-42f5-8acf-bb98822c8fef

for any additional errors or warnings that could provide more insights. This can help in identifying if there's a specific step or process where the error is triggered. If the issue persists, reviewing the exact payload and response involved in these calls can help in pinpointing the exact cause. Make sure that your implementation aligns with the guidelines provided in the Vapi documentation regarding call forwarding and error handling , [(1)]() . If you need further assistance with the specific details of the error, you might consider directly examining the detailed logs or error messages if available from the Vapi dashboard or API responses.