This paper shows the first results of a prototype implementation of a generative urban design tool. This implementation will form part of a design support tool for a GIS based platform defined to formulate, generate and evaluate urban designs. These three goals, formulation, generation and evaluation are integrated by connecting three modules developed individually for each goal. In this paper we focus on the implementation of the generation module showing a prototype developed on the Integrated Development Environment (IDE) of AutoCAD Civil 3D. This implementation attempts to encode the design moves of the urban planner into design patterns supported on grammar formalisms which allow for design synthesis and design exploration in the field of urban design.