A method for improving searches in a peer-to-peer (P2P) file sharing system that includes a plurality of server computers. A content file, identified by a descriptor including at least one metadata term and a mathematical identifier that uniquely identifies the content file in one of the server computers, is selected for searching. Other server computers are searched to find one or more matching content files; one that has a descriptor with a mathematical identifier matching the mathematical identifier of the first content file. The descriptors of the matching content files are returned to the searching server computer and used to expand the local descriptor.