The CNCjs MCP Server bridges Claude Code to CNCjs for controlling GRBL-based CNC machines, covering machine monitoring, connection management, motion control, job execution, and design/G-code generation.
Machine Control & Monitoring
List serial ports, connect/disconnect (specify port, baud rate, controller type)
Query machine state, positions (machine & work coordinates), work offsets, GRBL settings, parser state, job progress, workflow state, feeder status, alarms, and console output
Send raw G-code commands, load G-code files, and analyze G-code
Start, pause, resume, and stop jobs
Home the machine, unlock alarms, jog axes incrementally
Set feed rate and spindle speed overrides (10–200%), set work zero, control spindle/coolant, set WCS, and run Z probing
List and execute CNCjs macros; list machine profiles with travel limits
Safety Operations
Emergency stop (GRBL soft reset), feed hold, and jog cancel
G-code Generation
Generate G-code for 2D profiles, rectangular/circular pockets, drilling patterns, and surface facing/leveling
Design File & CAD/CAM Integration
Create SVG and DXF R12 files for import into CAM software
Generate Fusion 360 Python API scripts (sketch, extrude, revolve, CAM setup)
Generate FreeCAD Python scripts for 3D modeling and CAM toolpaths
Generate Adobe Illustrator ExtendScript (.jsx) for vector artwork and batch export
Marketplace & Packaging
Bundle designs into packages with multiple formats, previews, and metadata
Generate SEO-optimized listing descriptions for platforms like Etsy, Cults3D, or Gumroad
Convert between design formats (SVG↔DXF, G-code→SVG preview)
Click on "Deploy Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type @ followed by the MCP server name and your instructions, e.g., "@CNCjs MCP Server Home the machine and report the current work coordinates"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
MCP server bridging Claude Code to CNCjs for GRBL CNC control (FoxAlien XE Ultra).
Claude Code ←stdio/MCP→ cncjs-mcp (Node.js) ←Socket.IO v1→ CNCjs :8000 ←USB Serial→ GRBLRelated MCP server: MCP 3D Printer Server
list_serial_ports, get_connection_status, get_machine_state, get_machine_position, get_work_coordinate_offset, get_machine_settings, get_parser_state, get_loaded_gcode, get_job_progress, get_workflow_state, get_feeder_status, list_macros, list_machines, get_alarm_info, get_console_output, get_error_info, analyze_gcode
connect_to_port, disconnect_port
send_gcode, load_gcode, start_job, pause_job, resume_job, stop_job, home_machine, unlock_machine, jog, set_feed_override, set_spindle_override, set_work_zero, spindle_control, coolant_control, set_wcs, probe_z
emergency_stop (soft reset 0x18), feed_hold, jog_cancel
run_macro
generate_gcode_profile — cut 2D shapes (circle, rectangle, custom path)
generate_gcode_pocket — clear rectangular or circular pockets
generate_gcode_drill — drilling patterns (grid, circle, custom) with peck support
generate_gcode_facing — surface facing/leveling
generate_svg — create SVG files for import into Carveco/Fusion 360
generate_dxf — create DXF R12 files for CAM software import
generate_fusion_script — generate Python API scripts for Fusion 360 (sketch, extrude, revolve, fillet, chamfer, export, CAM setup)
list_fusion_scripts — list previously generated scripts
generate_freecad_model — generate Python scripts for headless 3D modeling (box, cylinder, sphere, cone, sketch, extrude, boolean ops, export STEP/STL)
generate_freecad_cam — generate CAM toolpath scripts with G-code export (profile, pocket, drill, face operations)
list_freecad_scripts — list previously generated FreeCAD scripts
generate_illustrator_script — generate ExtendScript (.jsx) for vector artwork (rectangle, circle, polygon, star, text, paths, export to SVG/DXF/PDF)
generate_illustrator_export_script — batch export current document to SVG/DXF/PDF/EPS with text-to-outlines option
list_illustrator_scripts — list previously generated Illustrator scripts
package_design — bundle designs into marketplace-ready packages (multi-format files, preview images, README, listing metadata, zip archive)
generate_listing_description — generate SEO-optimized listing descriptions for Etsy, Cults3D, or Gumroad
convert_design_format — convert between formats (SVG↔DXF, G-code→SVG preview)
Node.js (LTS recommended, v18+) — download from https://nodejs.org
CNCjs — install via npm after Node.js is set up:
npm install -g cncjsOr download the desktop app installer from the CNCjs GitHub releases page.
USB/Serial driver for your FoxAlien XE Ultra — likely one of:
CH340 driver (most common on FoxAlien boards) — download from the manufacturer site
CP210x driver (if it uses a SiLabs chip)
Windows 10/11 may auto-install these, but if your board doesn't show up in Device Manager under "Ports (COM & LPT)", install the driver manually
Quick start after install:
cncjsThen open http://localhost:8000 in your browser. Your FoxAlien will show up as a COM port (e.g., COM3). Select it, set baud rate to 115200, controller type Grbl, and connect.
Optional but recommended:
Chrome/Edge — CNCjs web UI works best in Chromium browsers
Python (sometimes needed for node-gyp native module builds during npm install)
npm install
npm run buildRegister with Claude Code:
claude mcp add cncjs-mcp node /path/to/cncjs-mcp/build/index.jsCNCJS_URL — CNCjs server URL (default: http://localhost:8000)
CNCJS_TOKEN — Optional JWT token for CNCjs authentication
Open a serial connection to a CNC controller
Inputs: port (required), baudrate, controllerType.
Close the current serial connection
Inputs: no named parameters.
EMERGENCY STOP — immediately halts all motion via GRBL soft reset (0x18). Use in any dangerous situation.
Inputs: no named parameters.
Feed hold — controlled deceleration to stop. Safer than emergency stop for non-critical situations.
Inputs: no named parameters.
Get current alarm code and human-readable meaning
Inputs: no named parameters.
Get current CNCjs connection status
Inputs: no named parameters.
Get feeder queue depth, hold state, and reason
Inputs: no named parameters.
Get current job progress (lines sent, elapsed time, % complete)
Inputs: no named parameters.
Get currently loaded G-code file name and content
Inputs: no named parameters.
Get current machine and work positions (X, Y, Z)
Inputs: no named parameters.
Get all GRBL $$ machine settings with labels
Inputs: no named parameters.
Get full GRBL machine state (positions, feed, spindle, overrides, buffer)
Inputs: no named parameters.
Get active G-code parser state (WCS, units, distance mode, etc.)
Inputs: no named parameters.
Get work coordinate offset (WCO) values
Inputs: no named parameters.
Get workflow state (idle, running, paused)
Inputs: no named parameters.
Run GRBL homing cycle ($H). Machine must have homing switches enabled.
Inputs: no named parameters.
Jog the machine incrementally. HIGH RISK — causes physical motion.
Inputs: axis (required), distance (required), feedrate (required).
List machine profiles with travel limits
Inputs: no named parameters.
List all CNCjs macros (name, id, content)
Inputs: no named parameters.
List available serial ports
Inputs: no named parameters.
Load G-code content into CNCjs for execution
Inputs: name (required), content (required).
Pause the current job (feed hold + pause sender)
Inputs: no named parameters.
Resume a paused job
Inputs: no named parameters.
Execute a CNCjs macro by name or ID. HIGH RISK — macro content may cause motion.
Inputs: identifier (required).
Send one or more G-code lines to the machine. HIGH RISK — causes physical motion.
Inputs: gcode (required).
Adjust feed rate override (10-200%)
Inputs: value (required).
Adjust spindle speed override (10-200%)
Inputs: value (required).
Start executing the loaded G-code program
Inputs: no named parameters.
Stop the current job
Inputs: force.
Clear GRBL alarm state ($X). Use after resolving the cause of the alarm.
Inputs: no named parameters.
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
Loading tool schema changelog…
Scored across 30 tools
Most tools are clearly distinct (e.g., get_machine_state vs get_machine_position vs get_parser_state), but some overlap exists: get_machine_state, get_workflow_state, and get_connection_status all report status-like information, and get_loaded_gcode vs load_gcode could be confused at a glance. Descriptions help disambiguate, but a few boundaries are fuzzy.
The set predominantly follows a verb_noun pattern (list_, get_, set_, start_, pause_, resume_, stop_, home_, unlock_, jog, send_, load_, connect_, disconnect_). Minor deviations: 'jog' is a bare verb, and 'emergency_stop'/'feed_hold' are noun-ish verbs, but overall the pattern is consistent and predictable.
30 tools is on the heavy side for a CNC control server, but the domain is broad (machine control, G-code management, job lifecycle, macros, serial ports, overrides). Each tool maps to a real operation, though some could be consolidated (e.g., get_machine_state already includes positions, making get_machine_position partially redundant).
The surface covers the core CNC workflow well: connection, machine state, G-code loading, job control, homing, unlocking, overrides, and macros. Minor gaps include no tool for writing/saving macros, no spindle control (only override), and no coolant control, but these are not critical for basic operation.
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