{
  "type": "function",
  "function": {
    "name": "book_flight",
    "description": "Book a flight reservation",
    "parameters": {
      "type": "object",
      "properties": {
        "user_id": {
          "type": "string",
          "description": "User ID making the booking"
        },
        "flight_details": {
          "type": "object",
          "description": "Selected flight information",
          "properties": {
            "outbound_flight": {
              "type": "string",
              "description": "Outbound flight number"
            },
            "return_flight": {
              "type": "string",
              "description": "Return flight number (for round trip)"
            },
            "cabin_class": {
              "type": "string",
              "enum": ["basic_economy", "economy", "business", "first"]
            }
          }
        },
        "passengers": {
          "type": "array",
          "items": {
            "type": "object",
            "properties": {
              "first_name": {
                "type": "string"
              },
              "last_name": {
                "type": "string"
              },
              "date_of_birth": {
                "type": "string",
                "description": "Date of birth in YYYY-MM-DD format"
              }
            },
            "required": ["first_name", "last_name", "date_of_birth"]
          }
        },
        "payment_method": {
          "type": "object",
          "properties": {
            "certificates": {
              "type": "array",
              "items": {
                "type": "string"
              },
              "description": "Travel certificate IDs (max 1)"
            },
            "credit_card": {
              "type": "string",
              "description": "Credit card ID from user profile"
            },
            "gift_cards": {
              "type": "array",
              "items": {
                "type": "string"
              },
              "description": "Gift card IDs (max 3)"
            }
          }
        },
        "checked_bags": {
          "type": "integer",
          "description": "Number of checked bags",
          "minimum": 0
        },
        "travel_insurance": {
          "type": "boolean",
          "description": "Whether to add travel insurance"
        }
      },
      "required": ["user_id", "flight_details", "passengers", "payment_method"]
    }
  }
}