Shifting tool assembly that facilitates controlled pressure equalization

An exemplary downhole system includes a completion string positioned within a wellbore and providing at least an upper seal bore and a downhole device that includes a sliding sleeve. A service tool is extendable within the completion string and includes a shifting tool assembly and provides a mandrel, a shifting tool coupled to the mandrel, and upper equalization seals arranged on the mandrel and sealingly engageable with the upper seal bore. The shifting tool is engageable with the sliding sleeve to move the downhole device at least partially between a closed position, where a pressure differential between a subterranean formation and an interior of the completion string is assumed by primary sealing elements of the downhole device, and an open position, where the pressure differential is assumed by at least the upper equalization seals.