1. A computer-implemented method, comprising: receiving, from a computer device, a query that includes terms and that is in a format that is unstructured for a plurality of databases; receiving data identifying resources that are determined to be responsive to the query, each resource being associated with a search score that defines a respective position of the resource in an order of responsiveness to the query; determining, by a data processing apparatus, a selected service requirement from the terms of the query, the selected service requirement being selected from a plurality of service requirements fulfilled by the databases, the determining the selected service requirement from the terms of the query comprising: accessing data defining, for each of the databases, a service requirement fulfilled by the database and parameter types associated with the service requirement, each parameter type defining a parameter input type or parameter output type that the database receives as input or provide as output, respectively, for a search operation particular to the database that fulfills the service requirement; selecting, from the query, terms that define parameter values for parameter types associated with service requirements; and selecting the service requirement based on the terms that define parameter values for the parameter types of the service requirements; determining, for each of the databases, a service requirement score for the database, the service requirement score being a measure of an ability of the database to fulfill the selected service requirement, the determining comprising determining a first score based on matches of the parameter values defined by the terms to the parameter types of the service requirement fulfilled by the database and a quantity of parameter values of the matching parameter types in the database; for each resource that is associated with one of the databases, adjusting the search score based on the service requirement score for the database; generating search results, each search result identify a corresponding resource that was determined to be responsive to the query, and the search results being ordered according to the respective search scores and adjusted search scores of the resources; and providing the search results to the computer device according to the order in response to the query.