In addition to general information on the PSM, features can be added based on predictions, representing the similarity between the observed and predicted peptidoform properties, such as spectral similarity and retention time differences. Rescoring tools with only a few features use a single representative feature for each type, whereas more extensive feature sets include multiple related values as distinct features. The concept behind using such related features is that even when they exhibit some statistical correlation, they may not be completely redundant due to subtle variations in their information content and thus may still provide complementary signals to improve the predictive performance . For example, the more extensive feature set of MS 2 Rescore has been suggested as a possible driver of its performance . It is only when features are perfectly correlated that they are truly redundant, in which case adding them yields no additional information .