I have a tool with these configurations

{
  "id": "5d110d70-e10b-4ceb-b748-dbba84a9817c",
  "type": "transferCall",
  "function": {
    "name": "transfer_language_call_tool",
    "description": "Transfers the caller to the appropriate assistant based on their selected language. The language selected by the user, either 'english' or 'spanish'."
  },
  "messages": [
    {
      "type": "request-start",
      "content": "I am forwarding your call. Please stay on the line.",
      "blocking": false,
      "conditions": [
        {
          "param": "destination",
          "value": "+123",
          "operator": "eq"
        }
      ]
    },
    {
      "type": "request-start",
      "content": "I am forwarding your call. Please stay on the line.",
      "blocking": false,
      "conditions": [
        {
          "param": "destination",
          "value": "+124",
          "operator": "eq"
        }
      ]
    }
  ],
  "orgId": "273e41b7-c8cc-4500-a158-f0825dd805f4",
  "destinations": [
    {
      "type": "number",
      "number": "+123",
      "description": "if the caller wants to continue with English language",
      "transferPlan": {
        "mode": "blind-transfer",
        "sipVerb": "refer"
      },
      "numberE164CheckEnabled": true
    },
    {
      "type": "number",
      "number": "+124",
      "description": "if the caller wants to continue with Spanish language",
      "transferPlan": {
        "mode": "blind-transfer",
        "sipVerb": "refer"
      },
      "numberE164CheckEnabled": true
    }
  ]
}

09/23/2025 14:58 inboundPhoneCall call ID: b988fc72-e7b1-4e1d-998c-19a3aebd7e56 log information "id": "log-77", "level": 30, "time": 1758628704894, "timestamp": 1758628704894000000, the call should have been continued with the forwarded number but instead the call is disconnected after the tool execution, I attached the log for tool execution image https://cdn.discordapp.com/attachments/1420022372400107560/1420022372873797733/image.png?ex=68d3e264&is=68d290e4&hm=91830d63690ab8103e654de8399e3d97c5fdb06f361850a3f4c821854205a136&

Suggestion: Your

transferCall

tool may be missing the required

destination

property in its parameters, which is necessary for the call to forward successfully. Update your tool configuration to include a parameters section like this:

json
"parameters": {
  "type": "object",
  "properties": {
    "destination": {
      "type": "string",
      "enum": ["+123", "+124"], // Use your actual E.164 numbers
      "description": "The destination to transfer the call to."
    }
  },
  "required": ["destination"]
}

Add this to your tool definition and ensure your telephony provider supports SIP REFER for transfers. Sources: - [Vapi documentation: call forwarding](https://docs.vapi.ai/phone-calling/transfer-calls/debug-forwarding-drops) - [Vapi SIP Trunking Telnyx external number call forwarding troubleshooting (Discord)](https://discord.com/channels/1211482211119796234/1343963959421829172)

Thank you for the call id. We are reviewing the PCAP file