orcaslicer-mcp

Let an AI assistant like Claude work with OrcaSlicer and your OrcaSlicer code.

What is this? (plain version)

Claude and other AI assistants can only talk by default. An MCP server is a small helper program that gives them new abilities — like hands and eyes for a job.

This helper gives the AI two sets of abilities:

1. Work with your code. Look at your OrcaSlicer code, check what changed, read files, search the code, and check if your online tests passed.

2. Work with the slicer. Slice a 3D model into a print file, then read back how long it will take, how much filament it uses, and how many layers it has.

So instead of you clicking around, you can just ask: "Slice the Julia vase and tell me how long it takes," or "What changed in my code today?"

MCP stands for Model Context Protocol. It's just the name for the standard way AI apps plug into helper programs like this one.

Related MCP server: GitLab MCP Server

What you need first

Two halves — you may only want one. The slicing half works for anyone who has OrcaSlicer installed. The code half is only useful if you actually edit OrcaSlicer's source code yourself. If that's not you, skip Git and GitHub CLI below and ignore the ORCA_FORK_DIR setting.

These instructions use Windows paths, but this also runs on macOS and Linux — just use the equivalent paths.

Each of these is free.

No Git and only want slicing? Click the green Code button on the GitHub page, choose Download ZIP, and unzip it wherever you like.

How to install (step by step)

1. Download this helper

Open a terminal and run:

git clone https://github.com/Diterex/orcaslicer-mcp.git
cd orcaslicer-mcp

2. Find your Python

Do this before installing, so the package lands in the same Python your AI app will use. Run:

where python

That prints one line per Python on your PC. Copy the one that looks like a real install, for example C:\Users\YOU\AppData\Local\Programs\Python\Python312\python.exe.

Skip any line containing WindowsApps — that one is a Microsoft Store placeholder, not a real Python, and it will not work here.

If nothing prints at all, Python isn't installed. Get it from python.org and tick Add Python to PATH during setup.

3. Install the one package it needs

Use the exact path you just copied, in quotes:

"C:\Users\YOU\AppData\Local\Programs\Python\Python312\python.exe" -m pip install "mcp[cli]"

You should see Successfully installed mcp-... at the end.

Either version 1 or version 2 of that package works — this helper detects which one you have and adapts. You don't need to pick.

4. Tell your AI app about this helper

Your AI app keeps a settings file written in JSON — a plain-text format where every quote, comma, and bracket has to be exactly right. One missing comma and the app ignores the whole file with no error message, so copy carefully.

Where the file lives:

• Claude Desktop (Windows): press Win+R, paste %APPDATA%\Claude\claude_desktop_config.json, press Enter. If Windows can't find it, the file doesn't exist yet — open the %APPDATA%\Claude folder and create an empty text file with exactly that name.

• Claude Code: C:\Users\YOU\.claude.json in your user folder.

Easiest option (Claude Code only) — skip the file entirely. Run this with your two real paths and it edits the settings for you:

claude mcp add --scope user orcaslicer-mcp -- "C:\Path\To\python.exe" "C:\Path\To\orcaslicer-mcp\server.py"

Editing by hand? The whole file should look like this. If yours already has an mcpServers section with other helpers in it, add just the "orcaslicer-mcp" block and put a comma after the block before it.

{
  "mcpServers": {
    "orcaslicer-mcp": {
      "type": "stdio",
      "command": "C:\\Users\\YOU\\AppData\\Local\\Programs\\Python\\Python312\\python.exe",
      "args": ["C:\\Users\\YOU\\orcaslicer-mcp\\server.py"],
      "env": {}
    }
  }
}

Three things that trip people up:

• Use double backslashes (\\) in every Windows path. In JSON a single \ means "something special follows," so C:\Users reads as broken text. \\ means one real backslash. (Forward slashes C:/Users/... also work.)

• "type": "stdio" just means the app starts this helper and they pass text back and forth. Leave it as-is.

• "env" holds extra settings. Leave it empty ({}) for now — see Settings below.

5. Restart your AI app

Quit it completely and reopen it. On Windows, closing the window isn't enough — right-click the Claude icon near the clock and choose Quit, then start it again.

Did it work?

Ask your AI:

"List your orcaslicer tools."

If it names tools like orca_repo_info and orca_slice, you're done. In Claude Code you can also type /mcp to see which helpers are connected.

If it didn't work

Nothing here can damage your PC — a failed setup just means the AI doesn't see the tools. Retry as often as you like.

How to use it

Just talk to your AI normally. Here are things you can try:

• "What branch am I on and what's changed?"

• "Show me my last 5 commits."

• "Did my latest tests pass on GitHub?"

• "List the test models I can slice."

• "Slice that model and tell me the print time and filament weight."

• "Read the print file we just made and summarize it."

• "Slice this clay model — is it likely to slump?"

Not sure what you can slice? Ask "what models can I slice?" first — it lists what's in your models folder (see ORCA_CORPUS_DIR under Settings).

Where do the sliced files go? Into C:\Users\YOU\.orcaslicer-mcp\out, in a new subfolder for each run. Open them in OrcaSlicer or send them to your printer as usual.

Slicing takes time. A big model can take a minute or two, and the AI will look like it's just sitting there while it works.

To turn it off, delete the orcaslicer-mcp block from your settings file and restart — or run claude mcp remove orcaslicer-mcp.

The AI picks the right ability for what you asked.

Settings you can change (optional)

Good news: it finds most things by itself. It looks for OrcaSlicer in the usual places and on your system PATH (the list of folders Windows searches when you type a program's name), so you normally don't have to tell it where the slicer is.

Two settings are worth knowing about:

• To slice your own models, set ORCA_CORPUS_DIR to the folder your models live in. For safety this helper only opens models inside that folder (plus its own output folder), so a model sitting in Downloads is refused with "path is outside the folders..." until you point this at it.

• To use the "work with your code" tools, set ORCA_FORK_DIR to the folder holding your copy of the OrcaSlicer source code. Skip it if you only slice.

You set any of these inside the "env" part of the config from step 4:

Example (inside "env": { ... }):

"env": {
  "ORCA_FORK_DIR": "C:\\Users\\YOU\\code\\OrcaSlicer",
  "ORCA_SLICER_EXE": "D:\\Programs\\OrcaSlicer\\orca-slicer.exe"
}

Is it safe?

Yes, by design. A few of these abilities don't just look — they change things, like sending your code to GitHub. None of those ever run by themselves.

First, the AI shows you exactly what it plans to do — and stops there. Nothing actually runs until you say yes (the AI has to run the tool a second time with your go-ahead attached). So it can't quietly push your code or open a request without you agreeing.

Also good to know: this helper runs on your computer with your permissions, the same as any program you start. Only install helpers you trust.

A few things it does to stay safe:

• Stays in bounds. It can only touch three folders: your OrcaSlicer folder, your models folder, and its own output folder. Everything else on your PC is off limits — which is also why you have to tell it where your models are before it will open them.

• Your text stays text. If you type something odd into a branch name or search box, it's treated as plain text, never as a secret extra instruction to run.

• Point it at code you trust. For the code tools, set ORCA_FORK_DIR to your own OrcaSlicer folder rather than running it inside a folder you downloaded from someone else.

The full list of abilities (tools)

Work with your code

These use Git, the tool programmers use to track changes. A quick primer: a branch is a separate line of work; a commit is a saved snapshot of your changes; upstream is the original OrcaSlicer project your copy came from; and a pull request (PR) is asking that original project to accept your changes.

Work with the slicer

Clay printing checks (LDM)

LDM stands for Liquid Deposition Modeling — printing with a paste like clay pushed through a nozzle, instead of melted plastic. Clay behaves differently: it can slump, tear, or collapse under its own weight, and you usually only find out after wasting an hour and a syringe of material.

The CeramicaSlicer version of OrcaSlicer checks your sliced file for those risks and writes down what it found. This helper reads that report back to you, so you can ask "is this print likely to slump?" before you start it.

When you slice a model that has clay mode turned on, you get two files instead of one:

• plate_1.gcode — the print file itself. G-code is the plain-text list of moves your printer follows, line by line.

• plate_1.gcode.ldm-analysis.json — a small companion report sitting right next to it, listing the risky spots.

You don't have to open either one. When you ask the AI to slice something, it reads the report and tells you the headline: an overall risk level, where the risk is concentrated, and any specific warnings. To look at an older print's report later, just ask — that's the orca_read_analysis tool.

Two things must both be true, or you get no report

1. You need the CeramicaSlicer version of OrcaSlicer. A fork is a copy of a project with someone's own changes added. The clay checks live in the CeramicaSlicer fork, not in the OrcaSlicer you download from the official site. On the regular public OrcaSlicer your model slices perfectly fine — you just get no clay report, because that version doesn't know how to write one. This helper looks inside your fork's build folder for orca-slicer.exe and uses it automatically; if your copy lives elsewhere, point at it with ORCA_SLICER_EXE.

2. Clay mode must be switched on inside the model file. This is a setting saved in the 3MF file, not something this helper turns on. A model with clay mode off slices normally and produces no clay report — that's correct behavior, not a bug. Worth knowing: the case-study files in CeramicaSlicer/corpus/*.3mf all have clay mode off, so they never produce a report. The ready-made clay-on test models are in your fork under tests/data/clay_corpus/, with names ending in _clay.3mf.

Sliced something and got no report? The tool tells you which of these two is missing — check its analysis_absent_reason before assuming anything is broken.

Works alongside OrcaSlicer's built-in helper

OrcaSlicer is adding its own built-in MCP helper (PR #12667) that controls the app while it's open — screenshots, the 3D view, live settings. That one and this one work well together:

• This helper works with your code and can slice without opening the app.

• The built-in one controls the open app (screenshots and the 3D view).

You can turn on both.

License

MIT — free to use, change, and share. See LICENSE.