Given raw a MS run in the mzLite or mzml format, this tool iterates accross all recorded MS/MS scans and determines the charge state of precursor ions which were selected for fragmentation. With this it is possible to query the peptide data base for every precursor ion mass +/- a tolerance (which defines the so called 'search space') and retrieve peptides that are theoretical candidates for a match. For each of the peptide candidates we create an theoretical spectrum in silico and compare it to the measured MS/MS scan.