We observed 139 Checkmol descriptors in at least two molecules in the set. We compared the proportion of molecules exhibiting some descriptor within the set to the proportion of molecules exhibiting the descriptor in the total set (Equation ). We can then identify descriptors that are over-represented or underrepresented within the set. The most over-represented descriptor within the set was the azo compound descriptor ([R]/N=N/[R], 717, 1500) which was over-represented in the set by a factor of 13.74. Such compounds have been a focus of reparameterization efforts in more recent versions of SMIRNOFF-based force fields, in particular in OpenFF 1.1. , consistent with our observation here that these may be poorly treated. We discuss later OpenFF releases further below. Four other descriptors were over-represented in the set by a factor greater than 4: