The correct interpretation of magnetic properties in the weak-exchange regime
has remained a challenging task for several decades. In this regime, the
effective exchange interaction between local spins is quite weak, of the same
order of magnitude or smaller than the various anisotropic terms, which
\textit{in fine} generates a complex set of levels characterized by spin
intercalation if not significant spin mixing. Although the model multispin
Hamiltonian, \hms{} = \js{} + \da{} +\db{} + \dab{}, is considered good enough
to map the experimental energies at zero field and in the strong-exchange
limit, theoretical works pointed out limitations of this simple model. This
work revives the use of \hms{} from a new theoretical perspective, detailing
point-by-point a strategy to correctly map the computational energies and wave
functions onto \hms{}, thus validating it regardless of the exchange regime. We
will distinguish two cases, based on experimentally characterized dicobalt(II)
complexes from the literature. If centrosymmetry imposes alignment of the
various rank-2 tensors constitutive of \hms{} in the first case, the absence of
any symmetry element prevents such alignment in the second case. In such a
context, the strategy provided herein becomes a powerful tool to rationalize
the experimental magnetic data, since it is capable of fully and rigorously
extracting the multispin model without any assumption on the orientation of its
constitutive tensors. Finally, previous theoretical data related to a known
dinickel(II) complex is reinterpreted, clarifying initial wanderings regarding
the weak-exchange limit