Abstract: The present invention provides an API that can be modified by a user using a parametric function of an automatic CAD system with a parametric function. The API passes information to the parametric engine of the auto-design CAD system and receives constrained conditions for a parametric graphic design described in a general script to pass it to the parametric engine. In other words, the API passes the information to the parametric engine of the auto-design CAD system and receives the information inputted from a sheet of a spreadsheet program to pass it to the parametric engine.