awv-informatik/classcad-ai/classcad

ClassCAD

ClassCAD is a headless CAD engine. The ClassCAD MCP runs it on this machine and gives you a live modeling session. You build a model by writing JavaScript programs against its API, you run them with run_script, and you prove the result with numbers and renders.

First use: sign in once

The MCP works with a free classcad.ch account, once per machine. If a tool answers "Sign-in required", the sign-in page has already opened in the user's browser. Show the user the link from that answer as a clickable link on its own line, then call login: it waits and returns as soon as they have signed in. Then repeat the call.

How to build a model

1. Read the input. A plain description, a dimensioned drawing, or a photo each need a different approach. A drawing with dimensions is rebuilt with constrained sketches, not hardcoded coordinates.
2. Plan the whole build, then fetch every document you need in ONE docs call: the matching recipe first, always recipes/verification, for an assembly or any model of several parts also recipes/clean-construction, then the methods (list_methods searches them). The server's own instructions name the recipes.
3. Build in a few substantial scripts, in a drawing of your own. Every tool that works on a model takes drawing: pass "new" with the first call of a model, and the answer names the drawing's id; pass that id in every further call about it. State persists between scripts: a follow-up script finds the part with await api.tree(). Never call part.create twice in one drawing. A new, unrelated model gets a drawing of its own ("new" again); clear starts over in the drawing you name.
4. Verify with numbers. part.calculateMassProperties after the last operation: compare the volume with what the design math predicts. A render that looks right is not proof. Measure parts, templates and the root assembly — never a single instance: that materializes every instance, and after saving the apps no longer draw them.
5. Show the result. Every drawing has a live CAD app (Buerligons), docked into the same engine: it comes up with the first model and follows every change. The result of that script ends with App: <link> and says where to open it; after that, view brings it back. snapshot renders stills (iso, sections, technical drawings in first- or third-angle): pass an outDir the user can open and hand them the image.
6. Work together. The user can work in the app too — select, measure, edit values and sketches, add features. It is the same model: read the tree again before relying on ids from before their turn. When they point instead of naming ("this face"), get_selection says what they selected.
7. Deliver. save writes STEP (format: "STP"), STL, GLB or OFB (ClassCAD's own format, with the features) to a path on disk: give the user that path. load opens such a file from its path. The app's File menu saves and opens them too. For their own app, website or configurator around the model, call account first (their plan decides where it may run), then follow recipes/buerli-app.

Good to know

• checkpoint before a risky step (large booleans, patterns), restore if it goes wrong.
• tree, find and inspect show the model structure; session_info shows the engine and the sign-in.
• The engine is the same one that runs in ClassCAD apps, so scripts written here carry over.
• More: https://classcad.ai and https://classcad.ch/docs/