Blog · · Andrii Shylenko

AI CAD for coding agents: from a prompt to checked STEP and STL

A 3D rendering is not a CAD deliverable. Before you print a bracket or send a part to a machine shop, you need editable geometry, known dimensions, and a file you can inspect. kernelCAD gives coding agents a source-based CAD workflow instead of stopping at a picture.

How it works

  1. Describe the part and its constraints. Give sizes, required holes, mating components and manufacturing process.
  2. Have the agent create editable .kcad.ts source, then evaluate the geometry.
  3. Inspect the model in 3D. Check dimensions, clearances and relevant manufacturability rules. Revise the source when a check fails.
  4. Export STEP for downstream CAD/CAM, STL for slicing, or a drawing PDF for review.

Use kernelCAD in ChatGPT, Claude, Claude Code, Codex, Cursor or VS Code. The hosted MCP endpoint is https://mcp.kernelcad.com/mcp. You can also run the open-source local MCP server: npx -y kernelcad mcp with Node.js 22.12 or newer.

Example: a lightweight honeycomb bracket

The honeycomb bracket source has editable thickness, cell size and web parameters. It is not a text-to-image example: the model was generated through the agent authoring loop, inspected and revised. Watch the turntable.

Its published verification notes report an FDM gate passing for a 2 mm minimum wall and no unsupported overhang, followed by STEP B-rep export and readback. Those are checks of the recorded example, not promises that any new prompt will pass.

Try this prompt in an agent connected to kernelCAD:

Design a printable L-bracket with a honeycomb lightening pattern.
Keep dimensions, lattice cell size and wall thickness as editable parameters.
Evaluate the model. Check printable wall thickness and overhangs.
Show the results and any failures. Revise the model if needed.
Export STEP and STL only after the checks are reported.

To reproduce the existing reference from a checkout with the CLI installed:

kernelcad evaluate showcase/honeycomb-bracket/honeycomb-bracket.kcad.ts
kernelcad dfm showcase/honeycomb-bracket/honeycomb-bracket.kcad.ts
kernelcad export step showcase/honeycomb-bracket/honeycomb-bracket.kcad.ts -o bracket.step
kernelcad inspect step bracket.step

Why this is different from one-shot AI CAD

A generated screenshot can look right while the underlying geometry is wrong. Here, the source, parameters, diagnostics and exported files remain available for review. You can tell the agent to change a thickness, fix a collision or recheck an assembly without starting from a new image.

For larger examples, the agent workflow replays show actual local tool output, including geometry checks and exports. The rocket engine routing example demonstrates a more complex workflow with a deliberately introduced line collision and its repair.

What these checks do not prove

A passing geometry or printability check does not certify load capacity, strength, fatigue, tolerances, or shop acceptance. Check critical dimensions, materials and manufacturing assumptions against the actual hardware.

Connect an agent or open kernelCAD Studio to try your own part.

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