As an evolution of CAD, KBE (Knowledge Based Engineering) concept represents today a strategic tool for product development improvements at aeronautics and automotive companies. At EMBRAER, KBE proved to be successful in reducing both product development cost and time by embedding engineering rules and processes. In this context and having in mind the RPA (Rapid Prototyping Application) philosophy, the RTDS (Rapid Tooling Design System) KBE application was developed. RTDS is an easy-to-use application for automated tooling design, mold design for either composite parts or sheet metal parts for the Embraer jet family EMBRAER 170. The application takes as input the part geometry and, by automating repetitive and insulated design tasks, generates the mold design for further fabrication through manufacturing process. Surfaces representing the mold design are generated and converted to a CAD software in order to build a closed volume. Acting on the bottle-neck of the mold design development cycle, the application provided reductions in both design cost and time.