find_cheapest_fare
Cheapest fare between two cities
Returns the cheapest observed one-way fare between two cities, plus the six-month low and the departure date on which the low was observed. Use whenever the user names an origin and a destination and asks about price, the cheapest date to fly, or whether a fare is a good deal. Both arguments are required; neither alone produces a valid answer. Answers are directional and per pair - PAR to BKK is not BKK to PAR and is not PAR to SIN. Prices are cached snapshots, never live quotes: say "last observed", never "current price", and surface live_check_url to any user about to book.
to必填from必填