text-to-cad-harness — Claude Code skill: CAD models from text
This skill has your coding agent write build123d Python parts from a description, export them as STEP, STL or URDF, and open the geometry in a local viewer.
npx skills add reason-machines/trending-skills --skill text-to-cad-harness -a claude-codeWhat text-to-cad-harness does
The agent edits scripts under models/*.py; the skill rebuilds the artifacts — STEP, STL, DXF, GLB and snapshots. Three pieces ship with it: skills/cad/ for parts and exports, skills/urdf/ for robot descriptions with links and joints, and viewer/, a React/Vite app that needs no backend. Geometry runs on build123d over OpenCascade (OCP).
Setup is the part people trip on. You need Python 3.11+ and a virtualenv: python3.11 -m venv .venv, then ./.venv/bin/pip install -r requirements-cad.txt. Skip that file and the model scripts will not run at all. The viewer starts with npm run dev from viewer/ and serves at http://localhost:4178.
Keep dimensions as variables such as OUTER_DIAMETER or HEIGHT and the agent changes numbers instead of rewriting geometry. Multi-part assemblies come together with Compound around several BuildPart blocks. The URDF side writes XML with link and joint entries plus meshes in meshes/.
What it helps with
- turn a written description into a 3D part
- export STEP and STL from one Python script
- build a parametric part driven by named variables
- generate a URDF robot with links and joints
- preview geometry in a browser with no backend
Example prompts for the agent
- Make an 80 by 60 mm bracket with four M6 holes and save it to
models/bracket/bracket.py - Generate a URDF for a robot with base_link and arm_link, revolute joint on the Z axis
- Change
HEIGHTon the hex spacer to 14 mm and rebuild the STEP file
How to install text-to-cad-harness
1Skills CLI (Vercel)
npx skills add reason-machines/trending-skills --skill text-to-cad-harness -a claude-code2Manually: put the files in place
~/.claude/skills/text-to-cad-harness/SKILL.mdCopy the whole skill folder; for one project use .claude/skills/text-to-cad-harness/
1Skills CLI (Vercel)
npx skills add reason-machines/trending-skills --skill text-to-cad-harness -a codex2Manually: put the files in place
.agents/skills/text-to-cad-harness/SKILL.mdFor all projects use ~/.agents/skills/
1Skills CLI (Vercel)
npx skills add reason-machines/trending-skills --skill text-to-cad-harness -a cursor2Manually: put the files in place
.cursor/skills/text-to-cad-harness/SKILL.mdCursor also reads .agents/skills/ and .claude/skills/
1GitHub CLI
gh skill install reason-machines/trending-skills text-to-cad-harness2Manually: put the files in place
.github/skills/text-to-cad-harness/SKILL.md1Skills CLI (Vercel)
npx skills add reason-machines/trending-skills --skill text-to-cad-harness -a gemini-cli2Platform CLI
gemini skills install https://github.com/reason-machines/trending-skills --path skills/text-to-cad-harnessManually: put the files in place
.devin/skills/text-to-cad-harness/SKILL.mdThe legacy .windsurf/skills/ path still works
Skills CLI (Vercel)
npx skills add reason-machines/trending-skills --skill text-to-cad-harness -a opencodeClaude.ai
Zip the folder and upload it in Settings → Capabilities → Skills
Step by step, with commands for each platform: How to install skills in Claude Code: five ways
Questions about text-to-cad-harness
How do I install text-to-cad-harness in Claude Code?
Run npx skills add reason-machines/trending-skills --skill text-to-cad-harness -a claude-code. The skill lands in ~/.claude/skills/text-to-cad-harness/SKILL.md.
What does text-to-cad-harness do?
It gives your agent instructions and scripts for writing CAD models in build123d, exporting them as STEP, STL, DXF, GLB or URDF, and viewing the result locally.
What do I need before using it?
Python 3.11+ with a virtualenv built from requirements-cad.txt, which pins build123d and OCP. The viewer also needs npm install inside viewer.
