Due to the considerable human intervention required, parameterizing a new small molecule force field can take decades . Evaluating choices in functional form or reference data used in different force fields is nearly impossible because these choices cannot be separated from the human intuition of the group who did the parameterization. Chemical perception, the way a force field determines which parameters to assign to a molecule, remains the limiting step in automating force field parameterization. Traditionally, force fields in the AMBER and CHARMM atom types to assign parameters. These atom types were assigned by hand making parameterization an extremely slow and tedious process. The Open Force Field Initiative is working to automate force field parameterization in the new SMIRNOFF which uses SMIRKS patterns to assign parameters. SMIRKS is a substructure language derived from SMILES . They describe molecular fragments by logically combining decorators for atoms (Table ) and bonds (Table ). However, the SMIRKS patterns in current SMIRNOFFs have been written by hand. Automating force field parameterization in the SMIRNOFF format requires automatic creation of these patterns as a part of the process.