build123d-mcp (pzfreo)
MCP server that lets an AI assistant build build123d CAD models in a persistent session, render previews, measure geometry, validate solids, and export STEP, STL, DXF and SVG instead of writing CAD scripts blind.
What it does and how it connects
build123d-mcp is a CAD toolbox that an AI or LLM app uses through MCP. It is not a standalone chatbot or CAD program. With an LLM app such as Claude, Cursor, VS Code, Continue, Cline, or Codex CLI, the assistant can create build123d CAD models, render previews, measure geometry, fix mistakes, and export STEP, STL, SVG, and DXF files.
The point of the tool, per the README, is that the assistant builds a part in small steps and checks the result as it goes, instead of writing a whole CAD script blindly. It runs as a local MCP server started by the AI app, with a browser only Codespaces trial and an HTTP mode for advanced self hosted deployments.
The README reports a benchmark result: on the public CADGenBench leaderboard in June 2026, using build123d-mcp raised the same model score from 0.360 to 0.457 and CAD validity from 88 percent to 100 percent. Python 3.11 through 3.14 are supported.
What engineers report
With build123d 0.13.0 forced in, health_check reports render_png failing, and measure, cross_sections, validate and render_view fail or report false validity failures.
2026-10-14Read the original
Alternatives
Compare side by side- Agent-CAD
A full AI CAD workbench with 2D drawings and revisions built on build123d, rather than a toolbox the assistant uses through MCP.
- AnkusDrive
A CLI and MCP server that drives FreeCAD with FEM and CFD simulation, rather than a toolbox for build123d models.
- cad-gen (philinhphan/cad-agent)
Turns a technical drawing into CadQuery geometry with a self refine loop and vision model critic, rather than a build123d toolbox used step by step.
- C33D
A browser based research preview where an LLM authors designs as an editable node graph, rather than a build123d toolbox for an MCP client.
- MecAgent
A commercial desktop copilot that acts inside an open SolidWorks session, rather than an open source MCP toolbox for build123d.
Sources
Not verified
- Pricing: none stated on the repo.
- A named individual builder beyond the repository owner handle pzfreo
Last verified November 6, 2026. Listings are informational. The evidence score measures public, verifiable evidence and is not an endorsement or a compatibility claim.