The analysis of TM-GSspin uncovered correlations between ground state spins and the various features of TM complexes (e.g., metal OS, the number of d electrons, coordination number, geometry, and the relative metal radius measure introduced herein). While most of the relationships were already established, we quantified their validity across the board and exploited them to build rule-based decision trees to assign the ground state spin for first row TM complexes. The most relevant features were also used as inputs of random forest models, achieving an impressive 97 % cross-validated accuracy within the dataset.