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Quick start

b123d-print's MCP server is a plug-in that gives your AI assistant CAD tools: it can then design a part, look at it, check it for printing problems and save files for your slicer. It runs on your own computer, and setup takes a couple of minutes.

The easy way: ask your assistant

Paste this into your AI assistant (Claude Code, Claude Desktop, Cursor, Gemini CLI, Codex, …):

Install the b123d-print MCP server for me. It runs with
`uvx --from b123d-print b123d-print-mcp --workspace <folder>`
where <folder> is a folder for my parts, such as ~/parts.
Install uv first if it is missing (https://docs.astral.sh/uv/).
Add the server to your MCP settings, tell me when to restart you,
and after the restart check that its tools (list_parts, new_part,
build_part, ...) are available.

The assistant will probably ask to run a few commands (to install uv and to add the server). That is expected: say yes. Assistants that can't run commands, such as a chat-only app, will tell you the steps instead.

By hand

  1. Install uv, a small tool that fetches Python and everything else b123d-print needs. On macOS or Linux:

    curl -LsSf https://astral.sh/uv/install.sh | sh

    On Windows, in PowerShell (installs for your account only, no admin):

    powershell -ExecutionPolicy ByPass -c "irm https://astral.sh/uv/install.ps1 | iex"

    (Other ways: the uv install page.)

  2. Add the server to your assistant.

    claude mcp add b123d-print -- uvx --from b123d-print b123d-print-mcp --workspace ~/parts

    Settings → Developer → Edit Config, and add (change the folder to yours):

    {
  "mcpServers": {
    "b123d-print": {
      "command": "uvx",
      "args": ["--from", "b123d-print", "b123d-print-mcp", "--workspace", "/Users/you/parts"]
    }
  }
}

    On Windows the folder is written with doubled backslashes: "C:\\Users\\you\\parts".

    If it then says "uvx not found", put the full path from which uvx (Windows: where.exe uvx) as command.

    Cursor, VS Code, Gemini CLI, Codex and others: Connect your MCP client.

  3. Restart the assistant.

Then ask

"Design a 40 mm round spacer, 10 mm tall, with an M3 hole."

The assistant asks you to confirm the dimensions, designs the part, checks it and saves the files in your parts folder, under parts/<name>/out/ (for example ~/parts/parts/spacer/out/spacer.3mf), ready for your slicer.

The very first start downloads a few hundred MB (mostly the geometry engine) and can take a few minutes; later starts are fast. If your assistant gives up waiting, see Troubleshooting.

Pictures

The assistant checks its own work by looking at the renders and cross-sections it makes. Claude Desktop and Claude Code pass those pictures to the model; check your assistant's docs for others. Without it the print checks still run, but look at the PNGs in out/ yourself.

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