All of the different transfer call tools are not working for me right now. I set it up with only the mandatory fields, so destination number, but it does show me this error everytime i try to be redirected. On the number to be redirected to it does not even ring. What is the problem here? https://cdn.discordapp.com/attachments/1412852606300061746/1412852606543466647/image.png?ex=68b9cd06&is=68b87b86&hm=03e6fa2c9c437ddbce2a7997edbef01329e9dfce59e904cccff0334359c6441e&

It looks like your TransferCall tool may be missing the required

destination

property in its parameters, which is a common cause for transfer failures. Try updating your tool's parameters section as follows:

json
"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+1234567890"], // Replace with your external number in E.164 format
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

Update this in your tool configuration and test again. If the issue persists, check that your SIP provider supports SIP REFER for transfers. Source: - [Vapi documentation: call forwarding](https://docs.vapi.ai/call-forwarding)

no, that is not the problem. as you can see here, i do have a destination for my tool, which still keeps showning me the same error https://cdn.discordapp.com/attachments/1412852606300061746/1412858207629475950/image.png?ex=68b9d23e&is=68b880be&hm=4fecc81b50f14b9dc96f8a878a13f8cb255f399a9ff4cebba25781c0d2998884&

Hi, I am facing the exact same issue. my use case is that i want to make call to my customer and upon request i want the AI to transfer the call to a human agent but if the transfer fails for some reason then i want to reume the call with customer without ending the call. for this i am using transfer plan mode: warm-transfer-experimental

i mostly use the web interface of vapi, so i can not provide you with that much of a help there. But yes, i do get the problem with all the different transfer modes

yeah its fine, but can you like tell me even if i make a tool in vapi UI, the request-fail param doesnt work same goes for the fall back in transferplan. Although the request-start does. Do you have any idea what could be the reason?

Hi ShinyChee, If your call transfers are not working, here's a quick guide to troubleshoot: 1. Verify End Reason: Check the

endedReason

in your call logs. If it's not

assistant-forwarded-call

, review your assistant configuration. 2. Check Server Message Configuration: Ensure your assistant’s

serverMessages

does not include

"phone-call-control"

unless implementing custom transfer logic. It could be overriding Vapi's management. 3. Phone Call Provider Bypass: Confirm that

phoneCallProviderBypassEnabled

is set to

false

for Vapi to handle call transfers. 4. Validate Transfer Scenarios: Certain types of transfers may not be supported. For instance, web-to-phone transfers are not supported. 5. Telephony Provider Logs: Examine your telephony provider’s logs for transfer-related errors. You may need to check Twilio, Vonage, or others for issues with transfer execution. 6. SIP Calls: If applicable, analyze SIP packets using a tool like Wireshark. Look for "REFER" packets which indicate transfer requests to your SIP provider. For more detailed troubleshooting, refer to the [Debug call forwarding drops guide](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops). I hope this helps resolve the issue.