If you have tried to get an AI agent to make a real, editable 3D part, you have probably hit the same wall: it writes an STL or a pile of OpenSCAD, and the moment you want to change one dimension you start over. A parametric CAD tool with a feature timeline fixes that, and SolidCraft is one that ships with its own MCP server.
tangency-labs/solidcraft is an open-source parametric 3D CAD application written in pure Rust. Per the README you sketch, constrain and build solids on a parametric feature timeline, change a dimension and watch the model rebuild, and run it on desktop, in the browser, or let AI agents model through the built-in MCP server. This post walks through the setup for Claude Code and what to expect.
What SolidCraft can do today
The README calls it "early but usable for simple parts" and backs that with a number: 75 of 76 public reference parts match their analytic or FreeCAD-computed volume, area, centre of mass and bounding box. The one miss is a tracked bug.
The feature list is already broad:
- Sketches and constraints: lines, arcs, splines and text, solved by its own constraint solver, with parameter-driven dimensions.
- Features: extrude, revolve, sweep, loft, fillet, chamfer, shell, draft, holes, threads, patterns, mirror, split and combine, all on an editable timeline.
- Parameters and configurations with unit-aware expressions.
- Assemblies with joints, motion studies, interference checks and mass properties.
- Sheet metal with flanges, hems, fold and unfold, and flat patterns.
-
Files: STEP, IGES, 3MF, STL, OBJ and glTF in and out where supported, plus URDF export and its own
.scdesigns.
The important line for agent users is the last one in that list: the desktop app, browser app, headless CLI and MCP server all run the same commands. Whatever the agent does, you can open and edit by hand.
Step 1: install SolidCraft
Pick the build for your machine from the README:
- Windows: the MSI installer from the latest release. The Windows downloads are not signed yet, so SmartScreen asks you to choose More info, then Run anyway.
- macOS: the disk image (Apple silicon and Intel), signed and notarized.
- Linux: the AppImage, or the Snap:
sudo snap install solidcraft
- Browser: solidcraft.io/app, no install. Good for a first look, but the MCP server needs the CLI.
If you prefer to build from source with Rust:
cargo run --release -p solidcraft -- --sample # desktop app with a sample part
cargo run --release -p solidcraft-cli -- commands # the command registry
Step 2: add the MCP server to Claude Code
solidcraft-cli mcp is a Model Context Protocol server. One line registers it with Claude Code:
claude mcp add solidcraft -- solidcraft-cli mcp
Two modes are worth knowing. Run headless, the server keeps its own design session. Started with --connect, it drives the running desktop app so you can watch every feature appear on the timeline. For a first session, the connected mode is far easier to trust.
On older Windows installers the CLI is not on PATH. The README says to give the full path instead, which by default is C:\Program Files\SolidCraft\solidcraft-cli.exe.
Step 3: ask for a part with real parameters
The README's own demo is a good template for a prompt: a Raspberry Pi 4 case built from an empty design, with a sketch dimensioned from the board's parameters, extrude, fillet and shell, M2.5 standoffs patterned on the 58 by 49 mm hole rectangle, port cut-outs, vent slots and engraved text. Then the case height goes from 24 to 32 mm in Parameters and everything rebuilds.
So ask for parameters, not just a shape:
Create a box enclosure 90 x 60 mm with a height parameter of 30 mm,
2 mm walls (shell), 1 mm fillets on the outer edges, and four M3 standoffs
patterned on a 70 x 40 mm rectangle. Name every dimension as a parameter.
When it is done, change height in the Parameters panel yourself. If the model rebuilds cleanly, the agent built it the right way. Export STEP for a machinist or STL or 3MF for a printer.
Step 4: script it when you need repeatability
A SolidCraft script is a JSON list of the same commands the UI runs. You can run one headless and write a file:
cargo run --release -p solidcraft-cli -- run examples/bracket.json --out bracket.step
This is handy once the agent has produced a part you like: keep the command list in the repo and regenerate the STEP in CI instead of trusting a binary file.
What people are building with it
The builds we track on the SolidCraft page show where it fits:
- A skeptical CAD user designed and delivered a custom part for a paying client with no crash, citing the editable feature timeline, constrained sketches and clean STEP and STL exports.
- One user hit a "wire not closed" error on a simple sketch in FreeCAD, redid it in SolidCraft and had it working in two minutes.
- A hobbyist replicated a Telecaster body from PDFs with SolidCraft connected to desktop ChatGPT, then had it add bindings and a kill switch. The first run missed the wire holes between the pickup pockets, so check the model.
- Another builder made a bot that models in SolidCraft and used it to design printable armor that snaps onto 6-inch poseable figures.
Related tools
If you want text-to-CAD as a skill set for agents rather than a full CAD app, text-to-cad generates 3D CAD models from text and runs related manufacturing and drawing workflows locally. For organic shapes, scenes and renders instead of engineering parts, MCP for Blender connects Blender to an LLM the same way.
Caveats
- The project describes itself as early. Use it for simple parts first and check volumes and dimensions before you send anything to a shop.
- Agents still miss details, as the guitar body example shows. The parametric timeline makes fixes cheap, but you are the reviewer.
- This walkthrough follows the README and has not been run end to end by us.
Source repo: tangency-labs/solidcraft. License: MIT or Apache-2.0.
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