This study shows the efficacy of a new tandem mass spectrometry peak finding software, GAGfinder. GAGfinder works by iterating through all potential fragments of a given precursor composition and comparing a theoretical isotopic distribution to the peak heights found in a tandem mass spectrum. We used ten synthetic heparan sulfate oligosaccharide to test the effectiveness of the method and compare GAGfinder's performance to that of an averagine-based algorithm.