The BEST buildup evaluation shut-in tool enables efficient high-quality downhole data acquisition required for well testing and reservoir surveillance. Early stages of pressure buildup are dominated by the compressibility of the fluid in the borehole, known as a wellbore storage effect, and this can mask pressure responses characteristic of the formation. The BEST tool minimizes wellbore storage effects by shutting the well downhole. It further enhances the interpretability of the early buildup pressure data through its instantaneous valve shut-in action for more accurate characterization of the near-wellbore region.