Route properties include cost, volume, and structural complexity. The cost of a route is the sum of molecule and reaction costs calculated by the RouteCostScorer function in AiZynthFinder, following the cost measurement in Badowski et al. The volume is the number of intermediates that need to be synthesized in a route. The structural complexity is measured as the total SCSscore 19 value of these intermediates along the route. Volume measures the number of items involved in the synthesis process, whereas complexity evaluates the overall synthesis complexity of these items.