This paper addresses the design issue of a three-axis tool head with three-PRS parallel kinematics (P, R, and S standing for prismatic, revolute, and spherical joint, respectively) by considering their orientation capability and motion/force transmission. The content presented here is actually an improvement on the dimensional optimization of articulated tool heads with parallel kinematics, with emphasis on the three-PRS design to solve the problem of orientational capability. An index that can evaluate the effectiveness of the motion/force transmission is introduced. The orientation capability with which the mechanism has high motion/force transmission capability is then defined. The procedure searching the link lengths with which the mechanism has a high orientation capability and good effectiveness of motion/force transmission is finally presented.