  The holographic recipe for the calculation of decay constants is revisited.
Starting from the holographic 2-point function and using the fact that
normalizable bulk modes scale as $z^{\Delta-S}$, with $S$ the spin, we can
obtain a consistent expression that depends on the value of the mode at the
boundary, not the derivative. We apply our decay constant expression to other
AdS/QCD (static and dynamic) models proving its consistency. We also
demonstrated that our approach is equivalent to the usual holographic
prescription.
