ugs-mcp
MCP server for controlling CNC machines via Universal GCode Sender.
Lets Claude (or any MCP-compatible AI assistant) connect to a CNC machine, inspect G-code,
and issue motion commands — all through the UGS Pendant REST API.
⚠️ STOP. READ THIS FIRST.
This software controls machines that can damage equipment, destroy parts, and injure or kill people.
CNC machines move fast and don't know where your hands are. Before you use this:
If you skim the safety docs and something goes wrong, that's on you. We warned you.
What it does
- Connection tools — Connect/disconnect UGS to your CNC, troubleshoot serial port issues
- Status tools — Read machine state, position, feed rate, spindle speed
- Motion tools (token-protected) — Jog axes, home, return to work zero, run G-code files and macros
- G-code inspector — Translate G-code to English, safety check, cycle time estimate, tool list
Every motion command uses a two-step token protocol: Claude generates a token, shows it to you,
and the machine only moves when you read the token back. Claude cannot bypass this — tokens are
generated and validated server-side.
Requirements
- Universal GCode Sender 2.x (winder.github.io/ugs_website)
- UGS Pendant plugin installed and active (Tools → Plugins → Installed)
- Pendant running at
http://localhost:8080 (default)
- Python 3.11+
Installation
Via pip
pip install ugs-mcp
From source
git clone https://github.com/zackpeters93/ugs-mcp.git
cd ugs-mcp
pip install -e .
Claude Code setup
claude mcp add ugs-cnc ugs-mcp
Or from source (without pip install):
claude mcp add ugs-cnc /path/to/ugs-mcp/ugs_mcp/run_server.sh
Claude Desktop setup
In ~/Library/Application Support/Claude/claude_desktop_config.json:
{
"mcpServers": {
"ugs-cnc": {
"command": "ugs-mcp"
}
}
}
Or from source:
{
"mcpServers": {
"ugs-cnc": {
"command": "/opt/homebrew/opt/python@3.11/libexec/bin/python3",
"args": ["-m", "ugs_mcp.server"],
"cwd": "/path/to/ugs-mcp"
}
}
}
Configuration
Environment variables (all optional):
| Variable | Default | Description |
|---|
UGS_HOST | localhost | UGS Pendant host |
UGS_PORT | 8080 | UGS Pendant port |
MACROS_DIR | ugs_mcp/macros/ | Directory for saved G-code macros |
RAPID_SPEED_MM_MIN | 5000 | Rapid speed used in return-to-zero |
Copy .env.example to .env to customize.
The token system
Every motion tool uses a mandatory two-step confirmation:
Step 1 — Call the tool without a token. Claude shows you a preview (axis, distance,
resulting position, safety warnings) and a token like [A3F8B2C1].
Step 2 — Read the preview. If you agree, tell Claude the token. Claude calls the tool
again with confirmation_token="A3F8B2C1". The machine moves.
Tokens are generated server-side via uuid4(), expire in 2 minutes, and are single-use.
Claude cannot predict, fabricate, or reuse them. The only way movement happens is if you
type the token back.
Tools
See USER_GUIDE.md for the full tool reference with parameters, examples,
and typical workflows.
| Category | Tools |
|---|
| Connection | ugs_connect, ugs_disconnect, ugs_troubleshoot_connection |
| Status | ugs_get_status, ugs_get_job_status |
| Job | ugs_run_file, ugs_pause_job, ugs_cancel_job |
| Motion | ugs_jog, ugs_home, ugs_return_to_zero, ugs_set_work_zero |
| G-code | gcode_safety_check, gcode_estimate_time, gcode_translate, gcode_list_tools, gcode_save_macro, gcode_list_macros, gcode_run_macro |
Tested with
- SainSmart Genmitsu 3018 Pro (GRBL)
- UGS 2.x with Pendant plugin
- macOS / Python 3.11
Likely works with any GRBL-based machine. TinyG/FluidNC/Smoothieware untested.
License
MIT — see LICENSE.
No warranty. No liability. Read SAFETY.md.
