  Anomalous couplings of the $Z$ boson to top quarks are only marginally
constrained by direct searches and are still sensitive to new particle dynamics
at the TeV scale. Employing an effective field theory approach we consider the
dimension-six operators which generate deviations from the standard-model
vector and axial-vector interactions. We show that rare $B$ and $K$ meson
decays together with electroweak precision observables provide strong
constraints on these couplings. We also consider constraints from t-channel
single-top production.
