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Gx3 Cli MCP

by purinzan

Analyzes local GX Works3 MELSEC projects in read-only mode through CLI commands and MCP tools.

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Install Gx3 Cli MCP

Pick your client, then add it in one click or paste the config.

STDIOPython
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "purinzan-gx3-cli-mcp": {
      "command": "uvx",
      "args": [
        "gx3-cli-mcp"
      ],
      "env": {
        "GX3_7Z": "YOUR_VALUE_HERE"
      }
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

Values are written into the snippet above so you can paste it as is. They never leave your browser.

We couldn’t confirm it starts correctly

We ran the install command but it didn't respond within our test window — this can mean a slow first-time install rather than a real problem.

uvx gx3-cli-mcp

Process exited before answering initialize.

This is an experimental automated check and can have false negatives — missing environment variables, a slow cold install, etc. It doesn’t necessarily mean something’s wrong. Last checked 9d ago.

Overview

The purinzan/gx3-cli-mcp MCP server analyzes Mitsubishi Electric MELSEC projects stored in GX Works3 .gx3 files. It runs locally as a stdio MCP server and exposes read-only ladder-analysis tools, including coil tracing, cross-references, comment search, external-input analysis, and logic checks. Use it when an agent needs structured answers about an existing PLC project without opening GX Works3 or modifying project files. Live device reads are available only through the CLI with explicit MC Protocol/SLMP connection parameters.

Use cases

  • Trace why a PLC coil never turns on
  • Find where a MELSEC device is written or read
  • Search ladder logic by device comment
  • Identify conditions arriving from HMI or network communication
  • Compare GX Works3 project versions

Key features

  • Read-only GX Works3 .gx3 project analysis
  • Ladder coil and interlock tracing
  • Device cross-references and comment search
  • External-input and communication analysis
  • Dead-logic and project lint checks
  • JSON and SVG-capable CLI output

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked 1d ago

Recent health check succeeded.

6/6 checks healthy over the last 46d

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 8d ago via OSV.dev · gx3-cli-mcp (PyPI)

Adoption & maintenance

Factual signals from GitHub, npm, and our automated checks — not a rating.

GitHub stars8Stargazers on the source repository.
Last commit12d agoMost recent push to the default branch.
Install checkInconclusiveDidn't respond in our test window — often a slow first install.
Directory activity8 viewsConfig copies, upvotes, and views on AllMCPs.

How Gx3 Cli MCP works

What purinzan/gx3-cli-mcp MCP server does

The purinzan/gx3-cli-mcp MCP server reads local GX Works3 .gx3 projects and turns ladder data into queryable analysis results. It is intended for investigating existing Mitsubishi Electric MELSEC programs, especially when you need to understand why a coil does not turn on, where a device is used, or which conditions originate outside the PLC.

The analysis is read-only. It does not write changes to a project, connect to a PLC to modify values, or replace GX Works3. Results are advisory, so findings should be checked in GX Works3 and against the applicable equipment-safety process before changes are made to a real system.

How it works

The package installs both gx3-cli and gx3-mcp-server. The CLI can inspect a project directly, while the MCP process provides the same general analysis surface to an AI agent over stdio. A client can start it with the gx3-mcp-server command, or invoke python -m gx3cli.gx3_mcp_server when the console script is not available on PATH.

Projects can be prepared with doctor, then indexed with the lightweight index and cross-reference commands. The guide command examines the project and suggests which analysis commands to run next. Commands support JSON output for scripting and can write results to a file instead of standard output. When a .gx3 archive is supplied, the tool extracts it into a cache identified by its SHA-256 value and analyzes that copy.

Setup and configuration

Install Python 3.10 or newer, then run:

Terminal
pip install gx3-cli-mcp

A basic MCP configuration is:

config.json
{
  "mcpServers": {
    "gx3": { "command": "gx3-mcp-server" }
  }
}

For 7-Zip-style project containers, install 7-Zip or set GX3_7Z to the executable path. Encrypted containers are not decrypted; the documented alternative is to export the project folder from GX Works3. No environment variable is required for the normal installation.

Tools and capabilities

The purinzan/gx3-cli-mcp MCP server covers several project-review tasks:

  • Trace device logic and inspect interlocks to investigate coils that remain off.
  • Find where a device is written or read with cross-reference commands.
  • Render ladder content as rung text or a layout image, and calculate project metrics.
  • Search ladder comments instead of relying on an unknown device number.
  • Identify inputs arriving from physical signals, HMI activity, or network communication.
  • Detect dead logic and lint issues such as duplicate coils, multiple writers, operand-width problems, and type problems.
  • Compare project versions with regular or semantic diffs.
  • Check whether a project was read correctly with roundtrip.

The CLI also includes synthetic-project generation for trying the workflow without an existing project. A restricted command runner is exposed alongside the read-only analysis tools.

Limitations and notes

Coverage is limited to ladder data in local .gx3 projects. The software is unofficial and is not affiliated with Mitsubishi Electric. Live device values can be read with live-read over MC Protocol/SLMP, but this is CLI-only and requires explicit connection parameters; the stated MCP workflow remains project analysis rather than PLC control.

The tool does not decrypt encrypted project containers. If parsing fails, doctor is the first troubleshooting step. A failure-corpus command can capture a local regression sample without sending it elsewhere. The repository describes its licensing as source-available rather than open source: internal evaluation and company use are allowed, while redistribution, SaaS hosting, and inclusion in a paid product require written permission.

Read the full README View source on GitHub

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Frequently Asked Questions about Gx3 Cli MCP

purinzan/gx3-cli-mcp is an MCP server that connects AI agents to local Mitsubishi Electric MELSEC projects saved by GX Works3 as `.gx3` files. Its main tools provide read-only ladder analysis, including coil tracing, device cross-references, comment search, external-input analysis, dead-logic checks, and project comparisons.

Install it with `pip install gx3-cli-mcp` using Python 3.10 or newer. The package provides the `gx3-mcp-server` executable and the `gx3-cli` command. Configure an MCP client to start `gx3-mcp-server`, or use the Python module invocation if the executable is not on `PATH`.

No, purinzan/gx3-cli-mcp performs read-only project analysis and does not write back to `.gx3` projects. It also does not expose project-mutating commands. Analysis output is advisory and should be verified in GX Works3 before making changes to equipment.

Run `gx3-cli doctor --root project.gx3` first to check whether the project can be read. For 7z-style containers, install 7-Zip or set `GX3_7Z` to its executable path. Encrypted containers are not decrypted, so export the project folder from GX Works3 instead.

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