greetings folks I am not 100% if Vapi's transferCall feature works. I have a custom tool to transfer calls. Here's a beginning of how this tool registration

"id": "a8fba37c-529a-4dac-8d57-5f98ea09eb3c",
  "createdAt": "2025-01-30T00:45:30.043Z",
  "updatedAt": "2025-04-25T20:39:30.605Z",
  "type": "transferCall",
  "function": {
    "name": "redirectCall",
    "description": "Use this function to transfer the call to various contacts across different departments",
    "parameters": {
      "type": "object",
      "properties": {
        "destination": {
          "description": "The destination phone number for the call transfer",
          "type": "string",
          "enum": [
            "+14082066610",
            "+14089131082",
            ...
            "+19543426123",
            "+14709451018"
          ]
        }
      },
      "required": [
        "destination"
      ]
    }
  },
  "messages": [
    
  ],

The VAPI assistant shows that this function does get called. Here's an excerpt from "Call Log Messages":

{
  "role": "tool_calls",
  "time": 1748978304436,
  "message": "",
  "toolCalls": [
    {
      "id": "call_EK83vIO49iUXO2ndlOLl7eUl",
      "type": "function",
      "function": {
        "name": "redirectCall",
        "arguments": "{\"destination\": \"+14089131082\"}"
      }
    }
  ],
  "secondsFromStart": 39.142
}

but the actual call transfer does not happen. The calls simply hang up without additional messaging. Any idea what might be going on here? Thanks

Hey! To help track down this issue, could you share: - The call ID This would really help us figure out what went wrong!

The call ID is

2c054bcd-b342-4762-af0b-8c9d0e30883f

You have to remove the phone call control server message from your assistant server messages, and then it will work.

Thank you. The advice seems to have worked.