These cookies can be dry for a couple reasons, if you added too much flour to the cookie batter, or if they are over baked. To prevent them from being to dry use the spoon and level method for measuring the flour, by scooping the flour spoon by spoon into the measuring cup until its overflowing, then level it off at the top with the back of a butter knife. For baking the cookies, they should only be baked until the edges are firm.