In this talk I will discuss how Standard-Model constraints, for instance due to analyticity and unitarity, can be used to complement theory computations of hadronic observables. Such constraints can play a decisive role in the analysis of lattice-QCD results of exclusive as well as inclusive semileptonic B-meson decays. In the former case, the use of Bayesian inference allows for formulating a model- and truncation independent parameterisation of hadronic form factors. In the latter case, QFT constraints allow for tackling the computation of the inclusive decay rate for the first time.