build123d MCP — Claude Code MCP server for 3D CAD
Connects build123d CAD tools to an AI assistant for modeling, geometry checks, and file export. Use it to build a part in stages and inspect the result along the way.
claude mcp add build123d-mcp -- uvx build123d-mcpWhat build123d MCP does
build123d MCP gives an AI assistant tools for creating CAD models with build123d. It can construct a part step by step, render a preview, measure geometry, correct mistakes, and export files in STEP, STL, SVG, or DXF formats. This is an MCP server, not a standalone CAD application or chatbot.
The AI app usually launches the server locally over stdio. Normal setup requires uv; the configuration example uses Python 3.12, and Python 3.11, 3.13, and 3.14 are supported too. In Claude Code, add the server command to the project’s .mcp.json or to ~/.claude/mcp.json, then restart the app. The setup command depends on uv, so make sure it is available first.
For imported STEP parts, the server can identify candidate holes and resize a plain through-hole, checking the geometry afterward. That edit path rejects holes with countersinks or multiple component faces. Those edits need to be made through execute() and checked against the resulting shape and STEP export.
What it helps with
- create a CAD part from a written description
- inspect a model with renders and geometry measurements
- export a finished model as STEP or STL
- resize a plain through-hole in an imported STEP part
Example prompts for the agent
- Use build123d MCP to create a mounting plate with holes, render it, and check its dimensions before exporting to STEP.
- Build the part in stages and verify its geometry before saving it as STL.
- Find a plain through-hole in the imported STEP model, resize it, and check the result.
How to install build123d MCP
Platform CLI
claude mcp add build123d-mcp -- uvx build123d-mcpuvx runs the command named after the package; if the README names another one, use uvx --from build123d-mcp <command>
Platform CLI
codex mcp add build123d-mcp -- uvx build123d-mcpuvx runs the command named after the package; if the README names another one, use uvx --from build123d-mcp <command>
Config file
{
"mcpServers": {
"build123d-mcp": {
"command": "uvx",
"args": [
"build123d-mcp"
]
}
}
}uvx runs the command named after the package; if the README names another one, use uvx --from build123d-mcp <command>
Config file
{
"servers": {
"build123d-mcp": {
"type": "stdio",
"command": "uvx",
"args": [
"build123d-mcp"
]
}
}
}uvx runs the command named after the package; if the README names another one, use uvx --from build123d-mcp <command>
Platform CLI
gemini mcp add build123d-mcp uvx build123d-mcpuvx runs the command named after the package; if the README names another one, use uvx --from build123d-mcp <command>
Step by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about build123d MCP
How do I install build123d MCP in Claude Code?
Run claude mcp add build123d-mcp -- uvx build123d-mcp, then restart Claude Code.
What does build123d MCP do?
It gives an AI assistant build123d tools to create and inspect 3D CAD models, then export them in CAD file formats.
What do I need to run build123d MCP?
You need uv and an app that supports MCP. The setup example uses Python 3.12; Python 3.11, 3.13, and 3.14 are supported as well.
