Gx3 Server

PyPI Python CI License gx3-cli-mcp MCP server

Work out why a coil never turns on, without opening GX Works3.

Reads a GX Works3 .gx3 project on your own machine and answers questions about it — where a device is written, what has to be true for a coil to turn on, which conditions come from outside the PLC, which branches can never be true. Read-only: it never writes back to the project.

It is a CLI, and the same analysis is a stdio MCP server, so an AI agent can answer from indexed facts instead of guessing at a binary file.

日本語: 三菱電機 MELSEC の .gx3 を GX Works3 を開かずに解析する CLI / MCP サーバーです。「このコイルがなぜ ON にならないか」をラダーから追います。 読み取り専用で、元のプロジェクトは書き換えません。

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Install

pip install gx3-cli-mcp

Python 3.10+. Installs two console scripts: gx3-cli and gx3-mcp-server.

Try it in 30 seconds

No project needed — generate one:

gx3-cli synthetic-project demo.gx3 --profile demo-line
gx3-cli guide --root demo.gx3

guide reads the project and tells you which commands are worth running on it, and why. That is the answer to "there are sixty commands, where do I start".

On a real project

gx3-cli doctor --root project.gx3        # does it read?
gx3-cli index-lite build --root project.gx3
gx3-cli xref build --root project.gx3
gx3-cli guide --root project.gx3         # what to run next

Then ask it something:

# where is this device written, and what reads it?
gx3-cli xref where-used M100 --root project.gx3

# why is this coil not turning on?
gx3-cli trace-device M100 --root project.gx3 --strict-logic --compact

# the whole program, one line per rung
gx3-cli rung-text --root project.gx3

# search the comment you remember, not the device number you don't
gx3-cli query-comment "clamp pressure" --root project.gx3

Every command takes --format json for scripting, and -o FILE to write instead of print. gx3-cli --help lists all of them by group.

Passing a .gx3 extracts it to .gx3_cache/<sha256>/ and analyses that copy.

What it can tell you

Question	Command
Why is this coil off?	trace-device, interlock-check
Where is this device written or read?	xref where-used, xref downstream
What does this program do?	rung-text, ladder-print, metrics
Show me the rung as a picture	ladder-layout --format svg
What comes from outside the PLC?	external-inputs, comm-refresh
What can never be true?	dead-logic
What looks wrong?	lint PROJECT (duplicate coils, multi-writer, operand widths, types)
What changed between versions?	diff, semantic-diff
Did it read the project correctly?	roundtrip

Use with an AI agent

{
  "mcpServers": {
    "gx3": { "command": "gx3-mcp-server" }
  }
}

Or "command": "python", "args": ["-m", "gx3cli.gx3_mcp_server"] if your client cannot resolve console scripts from PATH. The server exposes read-only analysis tools and a restricted command runner.

See Agent usage guide (JA) for how an agent should drive it.

Scope, honestly

Read-only analysis of .gx3 on your machine. Ladder is what it reads well. FBD, ST, SFC and MIL are detected and reported as such rather than guessed at, so a program it cannot read comes back saying so instead of coming back empty.

It does not edit projects, connect to a PLC to change anything, or replace GX Works3. live-read can read live device values over MC Protocol/SLMP, CLI-only and only with explicit connection parameters.

Output is advisory. Verify in GX Works3 and through your own safety process before touching real equipment. See Validation matrix (JA) for what has been checked.

If a project fails to parse, gx3-cli failure-corpus capture turns it into a local regression sample without sending anything anywhere.

Troubleshooting

7z-style .gx3 — install 7-Zip, or point at it: set GX3_7Z=C:\Program Files\7-Zip\7z.exe. Encrypted containers are not decrypted; export the folder from GX Works3 instead.

PyPI blocked — pip install git+https://github.com/purinzan/gx3-cli-mcp.git

Something reads wrong — gx3-cli doctor --root ... first, then open an issue.

Documentation

• User manual (JA) / (EN)
• Agent usage guide (JA)
• Ladder practical tips (JA) — field-oriented modification and review tips
• Security note (JA) — local data handling, read-only MCP policy
• Validation matrix (JA) — verified scope and limits
• GX Works3 feature matrix (JA) — standard-feature coverage, gaps, and implementation priorities
• File usage guide (JA) — repository map
• Analysis benchmark (JA) — synthetic performance baseline and measurement limits
• Review questions (JA) — the questions to ask a change before opening a pull request, and the bugs each of them found
• Related projects (JA) — other GX Works3/MELSEC tools and what was taken from them
• llms.txt — machine-readable summary of what this is and is not

Agent skills: existing project audit · failure corpus

Analysis contract migration

Current query-by-query status and remaining acceptance work for #153: 解析契約の移行台帳.

License

Source-available, not open source. Full terms in LICENSE.txt; this is a summary and the license text governs.

You may read the source and run it for evaluation and internal work, including inside a company. You may not redistribute it, host it as a service, or ship it in a paid product without written permission. There is no licence key, activation or paid plan.

日本語: 社内での評価・業務利用は許諾されています。禁止しているのは再配布、 SaaS 提供、有償製品への組み込みです。実行にライセンスキーや課金は不要です。 商用利用の相談は Issue からどうぞ。

Listed on Glama

Indexed as an MCP server, with per-tool scores for how well each tool describes what it does. Useful as outside feedback on the tool surface — the low scores there are the ones whose descriptions need work.

gx3-mcp-server on Glama

Contributing: CONTRIBUTING.md · AGENTS.md