  We introduce an $\imath \epsilon$ prescription for the SYK model both at
finite and at zero temperature. This prescription regularizes all the naive
ultraviolet divergences of the model. As expected the prescription breaks the
conformal invariance, but the latter is restored in the $\epsilon \to 0$ limit.
We prove rigorously that the Schwinger Dyson equation of the resummed two point
function at large $N$ and low momentum is recovered in this limit. Based on
this $\imath \epsilon$ prescription we introduce an effective field theory
Lagrangian for the infrared SYK model.
