This paper emphasizes the mechanism coordinator's role in coordinating the traders' information. When there are differences of opinions among traders on the valuation, there are cases in which efficient trading may not be undertaken. Efficiency can be achieved when the traders voluntarily design and agree on an efficient coordination mechanism. Nevertheless, if we consider an incompleteness of information among traders about subjective valuations, an information revelation problem may arise in the process of executing a mechanism. And some efficient coordination mechanisms may not be executable without the help of an objective third party. A mechanism coordinator can promote efficiency by executing a coordination mechanism.