There is no common standard on how to define a metal chelating group. For published libraries, like the commercial Life Chemicals and Otava libraries, or for the more focused academic library the details have not been revealed. [17] Alternatively, in MeDBA a rule-based algorithm has been used. Here, we first attempted to extract the MCS to cluster the retrieved ligands. As this proofed to be not successful, we then established a rule-based pipeline to make sure that all coordinating atoms were retained (Scheme 1). This resulted in chemically meaningful metal-chelating groups (Figure ). Yet, as the same ligand could be found with different binding modes in different structures, more than one chelating group could be extracted for the same or similar ligand. To visualize the relationship between the groups, a hierarchical tree was built in which each root or node represented a metal-chelating group that is contained in all groups in the nodes below (Figure ).