This book encourages tool building by laying bare the design of an excellent tool platform, Eclipse, and encourages design by building a typical tool extending Eclipse. This tutorial on creating custom tools also provides an explanation of a highly effective software design philosophy. The authors revive the lost art of supporting existing work by building tools. This book improves the software developers skill set by building little tools, and gradually growing those tools into better-than-professional quality products to help a whole community of developers. This book revives that highly-effective practice of tool writing and provides lessons along the way that tool building and design are two of the most leveraged skills for software developers.