The NPFC tool identifies natural product fragments present in the investigated compounds and analyzes their combination types by generating fragment combination graphs (FCGs). By comparing these graphs to those present in NPs , the tool classifies a given structure as either PNP, when it has FCGs that are not found in NPs; natural product like (NPL), when it has FCGs that are also present in NPs; NP, when the structure is identical to a NP; and finally, NonPNP for compounds that do not match any of these categories. When a compound has both PNP and NPL FCGs, it is classified as a PNP. Although the NPFC tool applies several structural filters, like number of rings > 0 and molecular weight < 1000, and deduplicates racemic structures after standardization by InChIKey before performing the analysis, parsing the output of the tool enables assignment of PNP-, NPL-, NP-and NonPNP status to a given set of compounds.