We then evaluated the impact of each feature on the model accuracy. As expected, removal of most of these features led to similar or slightly worse accuracy. Interestingly, removing atom size (entry 5, median MAE = 0.66) and hardness (entry 7, median MAE = 0.67) led to similar accuracies. As acidic atoms are mostly carbon, nitrogen, oxygen atoms, which are of similar size, and hardness is not directly linked to acidity, no drop in accuracy was expected while the slight improvement likely results from the simplification of the models. In contrast, removing ring size (entry 10, median MAE = 0.72) and the number of hydrogens (entry 11, median MAE = 0.72), two properties impacting pKa, led to significant drops.