Gear skiving is a technique proposed a long time ago for cutting internal gears at high productivity. Until recently, many problems have prevented its widespread use. With current technological breakthroughs, however, skiving is drawing attention again. The present paper describes cutting tool parameters, which could be vital for the optimum design of skiving cutters. Cutting tool parameters include depth of cut, rake angle, and clearance angle at each point on a cutting edge. They continuously change with progress in the cutting process. The parameters are defined on the basis of an oblique cutting model, which is a three-dimensional extension of an orthogonal cutting model. The example calculations in this study revealed the following features: Although rake angles almost always remain negative, clearance angles remain positive. At the points where clearance angles are large, depths of cut are large, but rake angles are small (i.e., largely negative). The decrease in shaft angle between the cutter and working blank axes increases depths of cut and clearance angles, while reducing rake angles (i.e., yields largely negative rake angles). Meanwhile, the increase in cutter tool face offset; i.e., the axial position of a tool face measured from a reference point on the conjugate pinion, narrows the area where depths of cut and clearance angles are small, but rake angles become largely negative. These parameters could be useful for evaluating tool cutting efficiencies in internal gear skiving.