For a QFT to be scale-invariant, its coupling parameters must be independent of the energy-scale of a given process, and this is indicated by the vanishing of the beta-functions of the theory.
Its coupling parameters must be independent of the energy-scale of a given process. This was for a QFT. This was to be scale-invariant. This is indicated by the vanishing of the beta-functions of the theory. This was for a QFT. This was to be scale-invariant.