Tool calling

{
  "message": "Check my current subscription",
  "userId": "user_42",
  "tools": [
    {
      "type": "function",
      "function": {
        "name": "check_subscription",
        "instructions": "Opens the customer's current subscription plan, renewal date, and payment status.",
        "parameters": {
          "type": "object",
          "properties": {
            "userId": { "type": "string", "description": "The customer's user id" }
          },
          "required": ["userId"]
        }
      }
    }
  ]
}

{
  "message": "What is the status of my account?",
  "userId": "user_42",
  "tools": [ /* same tool definitions */ ],
  "results": [
    {
      "toolCallId": "call_xyz",
      "output": "{\"plan\":\"pro\",\"status\":\"active\"}"
    }
  ]
}