In particular, the SMIRNOFF format is a relatively new chemical perception model that uses SMARTS patterns to assign parameters . The SMIRNOFF format specifies a sequence of SMARTS patterns and parameters are assigned according to the most recently matched SMARTS. The Open Force Field Consortium uses the SMIRNOFF format in its force fields, and the first implementation, called SMIRNOFF99Frosst 4 , was constructed by experts referencing the AMBER parm99 parameter set from Cornell et al. and Merck's parmFrosst force field. A strength of this approach is that extending the SMIRNOFF model is much simpler compared to traditional chemical perception models. Adding to a SMARTS chemical perception model just requires adding another SMARTS pattern. This is in contrast to traditional perception models, where a proliferation of new parameters must be defined to handle all new combinations of bonds, angles, and dihedrals that involve the new atom type. However, the difficulty of the SMIRNOFF format is that determining additional hand-written SMARTS for extending the force field has proven tedious, time-consuming, and often leads only to minimal improvements. A data driven, automated approach to determine SMARTS patterns is important for improving SMARTS chemical perception models.