Multi-turn tool-use scenario.
Tools involved: MessageAPI
TravelAPI

User requests (one per turn):
user: I'm setting sail on an adventure from Crescent Hollow to Rivermist and need the scoop on flight costs for my journey. My takeoff is scheduled for 2022-07-15, and luxury's the name of the game, so I'll be in business class.
user: Before diving into booking details, I need to establish my spending limits. Utilizing my access token 'access_token_abc123', I'll cap my budget at 2000 USD for the impending journey.
user: With the budget firmly in place, let's seal the deal! Employing my access token, book the flight using my credit card, identified with card7320, covering all associated flight expenses. I'll be traveling under Samuel Fisher, using my seasoned traveler number.
user: Once everything's set, I'd appreciate an invoice reflecting my recent flight procurement, giving me peace of mind about the particulars and expense.
user: I've hit a snag with the reservation process and would appreciate if you contacted customer support. Use my booking ID to express my 'Concerns regarding seating arrangements'.

Expected function call sequence:
TravelAPI.get_nearest_airport_by_city
TravelAPI.get_flight_cost
TravelAPI.set_budget_limit
TravelAPI.book_flight
TravelAPI.retrieve_invoice
TravelAPI.contact_customer_support
MessageAPI.send_message