Transition metal hydr(oxy)oxides (TMHs) are considered efficient electrocatalysts for the oxygen evolution reaction (OER) under alkaline conditions. Toward identification of potential descriptors to circumvent the scaling relation limit for the OER, first-principles calculations were used to quantify the effects on the overpotential of different s (Mg), p (Al), and d (Ti, V, Cr, Fe, Co, Sc, and Zn) electron dopants in Ni-based TMHs. Both the adsorbate evolution mechanism (AEM) and the lattice oxygen-mediated mechanism (LOM) were examined. The results demonstrate that the formation energy of oxygen vacancies (EVO) is strongly affected by the chemical nature of the dopants. A linear relationship is identified between EVO and the free energy difference for the oxygen-oxygen coupling. A descriptor could be employed to discriminate whether the LOM is energetically favored over the AEM. These findings fill existing gaps in appropriate yet computationally light descriptors for direct identification between the AEM and LOM.