1. A computer-implemented method for providing assertions in response to a travel item query, the method comprising: as implemented by one or more computing devices configured with specific executable instructions, receiving usage data reflective of user activity on a travel service, the user activity comprising a plurality of queries for travel items offered for by the travel service; for a set of search criteria, determining an assertion based at least in part on the usage data, wherein the assertion is associated with a modified set of search criteria determined based at least in part on a user activity, wherein the user activity is reflective of user action taken in response to a query corresponding to the set of search criteria; receiving, from a user computing device, a query corresponding to the set of search criteria; transmitting the determined assertion to the user computing device; receiving selection of the assertion by the user computing device; automatically modifying the query in accordance with the modified set of search criteria; and transmitting results of the modified query to the user computing device.