Multi-turn user requests:
user: List all international airports currently accessible for travel.
user: I'm based in Crescent Hollow. Determine which airport is closest to my location from the previously listed options.
user: I'm organizing a trip soon and need the flight cost from my nearest airport to Pinehaven on March 3, 2024, traveling in business class.

Tools involved: MathAPI
TravelAPI
Expected function-call sequence: TravelAPI.list_all_airports
TravelAPI.get_nearest_airport_by_city
TravelAPI.get_flight_cost
MathAPI.mean