Give trail (required without a partner key). The start times of a trail with the permits left for visitors at each one (as the trail page shows them: a number from 6 up, "few" at 1 to 5, "full" at 0), and a book_url per open start time that opens Reserve on madeira.fun at that time. Today up to 119 days ahead: give trail and date, or from and to (up to 14 days per call). Further ahead, up to 365 days: one trail and one date per call. Start times that have already begun today are never listed. Rate limited; a partner key (Authorization: Bearer mfk_...) gives higher limits, longer ranges and every trail at once (omit trail).