# build123d MCP

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.

- MCP server · `type=mcp` · Claude Code, Codex, Cursor, GitHub Copilot, Windsurf (Devin Desktop), Cline, Zed · ★ 130
- Author: pzfreo
- License: Apache-2.0 · policy=link-only · description only; the file stays with the author
- Source: https://github.com/pzfreo/build123d-mcp
- Updated: 2026-10-15
- HTML: https://affpapa.org/en/nevibecode/mcp/build123d-mcp

## What it 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.

## Requirements
- Needs: Python and uv (commands run via uvx)

## Install

### Claude Code (native platform)

**Platform CLI**
```bash
claude mcp add build123d-mcp -- uvx build123d-mcp
```
uvx runs the command named after the package; if the README names another one, use uvx --from build123d-mcp <command>

### Codex

**Platform CLI**
```bash
codex mcp add build123d-mcp -- uvx build123d-mcp
```
uvx runs the command named after the package; if the README names another one, use uvx --from build123d-mcp <command>

### Cursor

**Config file**
File `.cursor/mcp.json`:
```json
{
    "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>

### GitHub Copilot

**Config file**
File `.vscode/mcp.json`:
```json
{
    "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>

### Gemini CLI

**Platform CLI**
```bash
gemini mcp add build123d-mcp uvx build123d-mcp
```
uvx runs the command named after the package; if the README names another one, use uvx --from build123d-mcp <command>

## When to use it
- 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
- 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.

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