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

This happens because the tool is missing a destinations array, and the function name should be transferCall, not redirectCall. Update both and ensure the numbers match the enum.