Using band calculations within the FLAPS (full-potential linearized augmented-plane waves) model, information is obtained about the energy, charge, and spin characteristics of Pt$_{1-x}Me_{x}$MnSb alloys ($Me$ = Ni, Cu; $x$ = 0.0–1.0). As established, with an increase in the concentration of the nickel or copper atoms, the interatomic spatial density of electrons decreases, covalent bonds are weakened, and the binding energies of atoms in alloys decrease. As found, the dominant contributions to the formation of magnetic moments are made by 3$d$ electrons of manganese atoms, and the polarization of electrons at Fermi levels is dependent on the composition of alloys.