fusion360-mcp

Lets Claude Code drive Fusion 360: runs Python inside the live session with the full API available — build geometry, read dimensions, walk the timeline.

Leia em português

result = snapshot()
# doc: bearing.f3d  [mm]  sketches:7  timeline:16
# bodies: 11
#   outer_ring_flanged       173.978 mm3  17x17x4.6  faces:10
#   ball x7                    2.572 mm3  1.7x1.7x1.7  faces:1

Install

uvx fusion360-mcp install

Installs all three pieces: the add-in inside Fusion, the fusion360-api skill in ~/.claude/skills/, and the MCP entry in Claude Code.

Then in Fusion: Utilities → ADD-INS → Add-Ins, select "Claude MCP" and press Run. Tick Run on Startup to skip this next time. The add-in has to be running for the bridge to answer.

uvx fusion360-mcp status      # what is installed where
uvx fusion360-mcp uninstall   # take it back out

Close Fusion before installing — it holds the add-in files open. The installer detects this and tells you rather than corrupting the copy.

Requirements

• Fusion 360 (Windows or macOS)
• Claude Code
• Python 3.9+

No runtime dependencies: the MCP server speaks JSON-RPC using only the standard library.

How it works

Fusion only accepts API calls on its main thread. The add-in runs an HTTP server on a background thread and hands each request to the main thread via a CustomEvent; the HTTP thread blocks until the result comes back.

Claude Code  --stdio-->  server.py  --HTTP:8766-->  add-in  -->  Fusion

Requests carry a bearer token from ~/.claude-fusion-secret, created on first run. Without it any local process could execute Python in your Fusion session.

The tool

fusion_eval takes Python source and returns whatever you assign to result. adsk, app, ui, design and root are pre-bound, plus three helpers:

The skill

The package also installs the fusion360-api skill, which documents the API's traps — internal units in cm and radians, signatures that vary per feature, material names that follow the UI language. Every section came from a real mistake.

The skill is the part that compounds. Code gets written once; the traps keep being discovered, and each one someone writes down is a trap nobody after them loses an hour to.

Found a trap? Send it back

If the API surprised you, that's worth a PR. A method whose real name differs from the obvious one, a signature that changes per feature, an operation that fails silently, a value that only works in one unit — that is exactly what belongs in the skill, and it's the kind of thing no documentation lists because it only shows up in practice.

The bar is low on purpose. You don't need to fix anything or write well:

• Two calls are enough — the one that failed and the one that worked. Paste the real fusion_eval output, including the error message; that's what someone will search for when they hit the same wall.
• Say what you were building. Context separates a general trap from a one-off accident, and it's usually the difference between a note that helps and one that confuses.
• One PR per finding. Unrelated findings on separate branches review faster and don't block each other.
• Corrections beat additions. If something in the skill is wrong or went stale, saying so is more valuable than a new section — a skill that describes the tool wrongly is worse than an incomplete one. Put it in the title and it gets reviewed first.

The file is src/fusion360_mcp/skill/SKILL.md; the full rules are at the top of it. It's written in English so contributors anywhere can maintain it.

Not sure it's worth reporting? Open the PR anyway. Deciding is the maintainer's job, and an unreported trap costs the next person the same hour it cost you.

Contributing code

git clone https://github.com/artapo/fusion360-mcp
cd fusion360-mcp
python test_mcp_server.py    # passes whether Fusion is open or closed

The test runs without Fusion installed — it accepts either a live answer or "Cannot reach Fusion". CI runs it on Linux, macOS and Windows.

License

Apache 2.0 — as permissive as MIT, plus an explicit patent grant that protects both users and contributors.

Fusion 360 is a trademark of Autodesk, Inc. This project is not affiliated with or endorsed by Autodesk.