How to calculate the tokens when using function call

Thanks and further more;

namespace functions {

// Get the current weather in a given location
type get_current_weather = (_: {
// The city and state, e.g. San Francisco, CA
location: string,
unit?: "celsius" | "fahrenheit",
}) => any;

} // namespace functions

do we know where or how required fields ends up? (I now see the ? optional operator, thanks for the elaboration)