Fuente: WIPO "tomato" An online system performs an inference task in conjunction with the model serving system infer seasonality of items in an item catalog hosted by the online system. The online system generates and provides a prompt to a machine-learned language model to output a list of item categories predicted to be in season for a particular time period and a particular geographical location, e.g., associated with a requesting user. The language model outputs the list of item categories predicted to be in season. The online system validates the list by leveraging the language model and/or historical user engagement data. The online system maps items in the item catalog to the seasonal item categories and tags the mapped items with an in-season badge for display with the item in an ordering interface to the requesting user.