not much more than counting powers of $k$ and ${p_\text{typ}}$.

The situation is more complicated when some interactions must be treated non-perturbatively at leading order because of shallow real or virtual bound states with scales ${p_\text{typ}}\ll{\overline{\Lambda}_\text{EFT}}$ in the EFT’s range of validity. In $\mathrm{NN}$ scattering, all terms in the LO Lippmann-Schwinger equation, including the potential, must be of the same order when all nucleons are close to their non-relativistic mass-shell. If not, one term could be treated as perturbation of the others and there would be no shallow bound-state. Picking the nucleon-pole in the energy-integration, $q_0\sim\frac{q^2}{2M}$, leads to the consistency condition that both amplitude $T_\mathrm{NN}$ (ellipse) and potential $V_\mathrm{NN}$ (rectangle) must be of order $Q^{-1}$: $$\label{eq:consistency}
  \begin{split}
    \includegraphics[clip=]{consistentPC.pdf}
  \end{split}$$ In particular, the one-pion exchange appears to scale as $(\vec{\sigma}_1\cdot\vec{q})(\vec{\sigma}_2\cdot\vec{q})/(\vec{q}^2+{\ensuremath{m_\pi}}^2)\sim
Q^0$ when one counts only explicit low-momentum scales, but must be of order $Q^{-1}$ if its iteration is to be mandated. In a straightforward extension, amplitude and interaction between $n$ nucleons scale as $$\label{eq:consistency-n}
  T_{n\mathrm{N}}\sim V_{n\mathrm{N}}\sim Q^{1-n}$$ if it is nonperturbative at LO. Since both the interactions and the LECs themselves carry inverse powers of $Q$, finding their importance by counting momenta is insufficient. This result only assumes the existence of 