There has been a growing interest in measuring the cement bond quality quantitatively with LWD sonic tools. Recent studies have shown that quantitative cement evaluation with an LWD tool is feasible up to a certain bond index depending on conditions. In this paper we present several methods developed to identify the reliability of bond index computation with the current LWD sonic tools. The methods utilize information on the amplitude, transit time, and attenuation of the sonic waveforms acquired along a receiver array, as well as extensive modeling using the finite-difference method. The theoretical studies have been validated with real data recorded during some field test experiments that are also presented. The answer product based on these methods provides bond index values within the measurement range in conjunction with various quality control plots to provide confidence to the user on the validity of the answer.