{
  "_comment": "Vapi CUSTOM (function) tool, an alternative to the MCP server for operators who prefer a function tool. Add this to your assistant's tools. Vapi POSTs {message:{type:'tool-calls', toolCallList:[{id, arguments:{number}}]}} to server.url and expects {results:[{toolCallId, result}]}. Replace YOUR_API_KEY with a key that has the 'mcp' use case.",
  "type": "function",
  "function": {
    "name": "phone_lookup",
    "description": "Look up a phone number and return a supplementary, low-confidence intelligence bundle (validity, line type, carrier, country, caller name where available, a spam signal, and DNC / reassigned status). Advisory only — keep the routing decision.",
    "parameters": {
      "type": "object",
      "properties": {
        "number": { "type": "string", "description": "Phone number in E.164, e.g. +14155552671" }
      },
      "required": ["number"]
    }
  },
  "server": {
    "url": "https://numbers.online/api/v1/integrations/vapi/tool",
    "headers": { "Authorization": "Bearer YOUR_API_KEY" }
  }
}