[BFCL] Multi-turn TravelAPI book_flight() clarification

[kevins981]

Hi Gorilla/BFCL contributors,

Question regarding the book_flight() function:
The last input argument is travel_cost. It seems that there are two possible interpretations of this parameter:

1. travel_cost should be set to the price of the flight based on travel_date, travel_from, travel_to, travel_class. That is, the agent should first call get_flight_cost() to retrieve the cost of the flight, then call book_flight() with travel_cost equal to the flight cost.
2. travel_cost should be set to the cost specified by the user. In some cases, this user specified cost is not equal to the flight cost.

For example, the ground truth of multi_turn_base_152, multi_turn_base_155 use interpretation 1.

On the other hand, the ground truth of multi_turn_base_169 uses interpretation 2. Specifically, the user asks

I just relocated to Rivermist and I'm looking to book a flight to Los Angeles for a crucial business meeting. Could you arrange the flight for me, using my credit card with id 'card_6789'? I need it booked for next Friday 2024-11-10, in business class, with an estimated cost of approximately $1200.

The ground truth function call is book_flight(access_token='2278-9812-3456-4567', card_id='card_6789', travel_date='2024-11-10', travel_from='RMS', travel_to='LAX', travel_class='business', travel_cost=1200.0). Notice that the travel_cost used is $1200. The actual flight cost (obtained using get_flight_cost()) is only $660.

If both interpretations 1 and 2 are correct, perhaps it is clearer (to the model) if the travel_cost argument within book_flight() becomes optional? E.g. if not provided, travel_cost is set to the result of get_flight_cost(). Else, set it to the user provided custom value.

Best regards