Gemini Function Calling in ADK Java

public class WeatherTool implements Tool {
  @Override
  public String name() { return "get_weather"; }
  @Override
  public String description() { return "Get current weather for a city"; }
  @Override
  public Schema schema() {
    return Schema.object()
        .property("city", Schema.string().required())
        .property("units", Schema.string().enumValues("metric", "imperial"));
  }
  @Override
  public Object call(Map args) {
    return fetchWeather((String) args.get("city"));
  }
}