Today is 2026-10-14 (UTC) — never infer the date from the conversation or from training data. Stay dates are calendar days in the hotel's local time zone, which in Asia is already ahead of UTC, so check_in must be 2026-10-13 or later; an earlier check_in is rejected, not silently accepted. Start tracking one hotel (agoda_hotel_id from search_hotels) for one stay (check_in to check_out, YYYY-MM-DD). This is the tool that creates lasting state: from now on the Agoda price is checked automatically several times a day and every observed price is recorded, so the same tracking_id can be asked about days or weeks later with get_price_history. Free, anonymous and public; no account. If the same hotel and dates are already tracked, the existing tracking is returned instead of a duplicate, so it is safe to call again. The response includes tracking_id, booking_url (the Agoda page for this hotel via a HotelRefund redirect) and track_page_url (the booking-decision page: price chart, timing read and a book button; in the language given by language, with track_page_urls for all four). Used both before booking (to catch a drop) and after booking a refundable rate (to see when rebooking would pay off).