A shifting tool is provided for locating and actuating downhole tools in a downhole tubular string, such as sleeve valves spaced along a completion string. The shifting tool includes dogs at ends of two or more radially controllable, and circumferentially spaced support arms. The arms are manipulated with an axially movable arm-constrictor spider for engaging radially variable cams on the sides of the arms. The spider includes cam follower tabs to cam the arms radially inward for in and out of hole movement, and for releasing the arms for sleeve locating and sleeve profile engagement. The tabs are radially inset from the arms to minimize obstruction of a tool annulus and interference damage when travelling along the downhole string.