Chinese tone sandhi systems are often classified as left-dominant or right-dominant depending on the position of the syllable retaining the citation tone. An asymmetry exists between the two types of systems: left-dominant sandhi often involves rightward extension of the initial tone to the entire sandhi domain; right-dominant sandhi, however, often involves default insertion and paradigmatic neutralization of nonfinal tones. I argue that the extension of a tone to a larger domain may serve two markedness purposes: the reduction of tonal contours on a syllable and the reduction of pitch differences across syllable boundaries, both of which have a rightward directionality preference. The former is due to the durational advantage afforded by final lengthening; the latter is due to the universal preference for progressive tonal coarticulation. I show that a theory that formally encodes these preferences via intrinsic constraint rankings can predict the directional asymmetry noted above.