AI & text-to-CAD
KCL
Definition
KCL is Zoo's text-based programming language for parametric CAD. It is the source representation behind Zoo Design Studio models, so point-and-click actions and Zookeeper prompts can produce code that people can read, edit, reuse, and track with version control.
Also known as: KittyCAD Language, Zoo KCL
Updated
Why a CAD language matters for AI#
Zoo's KCL documentation describes it as KittyCAD's programming language for CAD and the source of truth behind Zoo models. Code is a format language models already generate well, so a CAD language gives text-to-CAD output that a person can read, diff, and edit instead of opaque geometry.
The KCL research overview explains that the language is functional and parametric. Designers can define reusable functions, named parameters, calculations, and assertions instead of storing only the final shape. That makes the design logic visible in a way a neutral geometry file is not.
One model, three editing methods#
Zoo Design Studio uses KCL whether the model is created with point-and-click tools, written directly in the code editor, or changed through Zookeeper. The May 2026 sketch-mode update added sketch blocks and access to Zoo's geometric constraint solver, so a KCL sketch can declare relationships and dimensions without spelling out every coordinate.
Those editing methods can be mixed. A designer can sketch with the mouse, clean up names and functions in code, then ask the agent to change a selected feature. The useful part is that the underlying model does not become a different kind of object each time the interface changes.
Portability has a boundary#
KCL is open source and plain text, which makes it suitable for diffs and Git-based version history. It is still specific to Zoo's modeling stack. To take the final geometry into another CAD program, you export it, usually as STEP. That neutral file carries the shape, not the KCL functions, parameters, and feature logic that generated it, so keep the KCL project when future revision matters.
Sources
Related terms
Text-to-CAD
Text-to-CAD is AI that turns a natural-language description into editable CAD geometry, such as a STEP file, a parametric model, or CAD code. The goal is a model with exact faces and dimensions that can be modified and manufactured, not just a shape that looks right on screen.
CadQuery
CadQuery is an open-source Python library for building parametric CAD models in code on top of the Open CASCADE kernel. It can export STEP as well as STL and 3MF, which makes it a common target when LLMs are asked to write CAD scripts.
OpenSCAD
OpenSCAD is free, open-source CAD software where models are written as code using constructive solid geometry and extrusion of 2D outlines. Because the whole model is text, it is one of the easiest CAD targets for LLMs to generate and edit.
AI-native CAD
AI-native CAD describes CAD software designed with AI as a core part of how geometry is created and edited, rather than an assistant added to an existing product. It is a marketing term without a standard definition, so claims should be judged by what the software actually does.
Geometric constraint solver
A geometric constraint solver calculates the positions and dimensions of sketch geometry so declared relationships, such as parallel, perpendicular, tangent, equal, coincident, and fixed dimensions, are satisfied together. It lets a designer define intent instead of calculating every coordinate by hand.
Parametric modeling
Parametric modeling builds a CAD model from dimensions, constraints, and an ordered list of features, so changing a value regenerates the geometry. It is the default approach in SolidWorks, Fusion, Onshape, Creo, NX, and FreeCAD Part Design.