Fusion 360 MCP Bridge for Claude

Connects Claude to a live Fusion 360 session via two MCP tools:

• fusion_execute — run any Python script inside Fusion with full adsk.* API access
• fusion_screenshot — capture the active viewport as a PNG for visual verification

Claude  ←→  MCP Server (Python)  ←→  Fusion Add-in (HTTP)  ←→  Fusion 360 API

The bridge is intentionally minimal — a thin connection layer. All Fusion API knowledge lives in CLAUDE.md, which Claude reads automatically at the start of every session.

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Requirements

Requirement	Notes
Fusion 360	Free personal licence is sufficient
Claude (Code or desktop)	See installation options below
Python 3.9+	macOS 12+ built-in; brew install python otherwise. Windows: python.org or winget install Python.Python.3

Installing Claude

Claude Code (CLI) — pick one:

# Homebrew (recommended on macOS)
brew install --cask claude-code

# npm
npm install -g @anthropic-ai/claude-code

# Official installer
curl -fsSL https://claude.ai/install.sh | bash

Note: Homebrew installs do not auto-update. Run brew upgrade claude-code periodically.

Claude desktop app (GUI): Download and install from claude.ai/download. MCP configuration differs slightly — see Configure the Claude desktop app below.

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Quick start (macOS)

Clone the repo anywhere you like, then run the one-shot setup script:

git clone https://github.com/ndoo/fusion360-mcp-bridge.git
cd fusion360-mcp-bridge
bash scripts/quickstart-mac.sh

The script installs Python dependencies, generates a shared secret token, copies the add-in into Fusion 360's add-in folder, and patches ~/.claude/settings.json automatically (Claude Code only — desktop app users see Configure the Claude desktop app).

After it finishes, follow the two manual steps it prints:

1. In Fusion 360 — Tools → Add-Ins (Shift+S) → select FusionMCPBridge → click Run (check Run on Startup to make this permanent).
2. Restart Claude so the MCP server is picked up.

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Quick start (Windows)

Clone the repo anywhere you like, then run the setup script from PowerShell:

git clone https://github.com/ndoo/fusion360-mcp-bridge.git
cd fusion360-mcp-bridge
powershell -ExecutionPolicy Bypass -File scripts\quickstart-windows.ps1

If you see a "running scripts is disabled" error, either use the -ExecutionPolicy Bypass flag shown above, or run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once.

The script installs Python dependencies (mcp + httpx), generates a shared secret token, copies the add-in into Fusion 360's add-in folder, and patches %USERPROFILE%\.claude\settings.json automatically (Claude Code only — desktop app users see Configure the Claude desktop app). No elevation/UAC is required — everything writes to user-owned directories.

After it finishes, follow the two manual steps it prints:

1. In Fusion 360 — Tools → Add-Ins (Shift+S) → select FusionMCPBridge → click Run (check Run on Startup to make this permanent).
2. Restart Claude so the MCP server is picked up.

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Manual installation

1 — Python dependencies

macOS — virtual environment (recommended with Homebrew Python)

python3 -m venv ~/venv
source ~/venv/bin/activate
pip install -r mcp-server/requirements.txt

The quickstart script and Claude settings will automatically use ~/venv/bin/python3 as the MCP server interpreter when that venv exists.

macOS — user install

pip3 install -r mcp-server/requirements.txt --user

Windows — user install

python -m pip install -r mcp-server\requirements.txt --user

2 — Generate shared secret

macOS

python3 -c "import secrets; print(secrets.token_hex(32))" > ~/.fusion-mcp-secret
chmod 600 ~/.fusion-mcp-secret

Windows (PowerShell)

python -c "import secrets; print(secrets.token_hex(32))" |
    Set-Content "$HOME\.fusion-mcp-secret"
# Restrict to current user (equivalent of chmod 600, no elevation needed)
$acl = Get-Acl "$HOME\.fusion-mcp-secret"
$acl.SetAccessRuleProtection($true, $false)
$acl.SetAccessRule((New-Object System.Security.AccessControl.FileSystemAccessRule(
    [System.Security.Principal.WindowsIdentity]::GetCurrent().Name,
    "FullControl", "None", "None", "Allow")))
Set-Acl "$HOME\.fusion-mcp-secret" $acl

Both the add-in and MCP server read ~/.fusion-mcp-secret at startup. The add-in rejects any HTTP request that does not carry a matching Bearer token, ensuring only the MCP server process (which holds the same file) can call /execute and /screenshot.

3 — Fusion 360 add-in

Copy the add-in folder into Fusion's add-in directory:

macOS

cp -r fusion-addin/FusionMCPBridge \
  ~/Library/Application\ Support/Autodesk/Autodesk\ Fusion\ 360/API/AddIns/

Windows

%APPDATA%\Autodesk\Autodesk Fusion 360\API\AddIns\

Copy the fusion-addin/FusionMCPBridge folder there.

Then in Fusion 360:

1. Tools → Add-Ins (or press Shift+S)
2. Select FusionMCPBridge under My Add-Ins
3. Click Run
4. A dialog confirms the bridge started and whether token auth is enabled

To start automatically on every launch, check Run on Startup.

4 — Configure Claude

Claude Code (CLI)

Add the mcpServers block to your Claude settings file (create it if it doesn't exist):

• macOS/Linux: ~/.claude/settings.json
• Windows: %USERPROFILE%\.claude\settings.json

{
  "mcpServers": {
    "fusion360": {
      "command": "python3",
      "args": ["/ABSOLUTE/PATH/TO/fusion360-mcp-bridge/mcp-server/server.py"]
    }
  }
}

On Windows, use python instead of python3, and backslash-escaped paths:

{
  "mcpServers": {
    "fusion360": {
      "command": "python",
      "args": ["C:\\Users\\you\\fusion360-mcp-bridge\\mcp-server\\server.py"]
    }
  }
}

Replace the path with the absolute path to your clone. Restart Claude Code — the MCP server starts fresh each session.

Configure the Claude desktop app

Open Claude → Settings → Developer → Edit Config and add the same mcpServers block to claude_desktop_config.json:

macOS — ~/Library/Application Support/Claude/claude_desktop_config.json Windows — %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "fusion360": {
      "command": "python3",
      "args": ["/ABSOLUTE/PATH/TO/fusion360-mcp-bridge/mcp-server/server.py"]
    }
  }
}

Save the file and restart the Claude desktop app.

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Verify the connection

With Fusion open and the add-in running:

# Health check (requires secret token)
curl -H "Authorization: Bearer $(cat ~/.fusion-mcp-secret)" \
     http://localhost:7654/health

Or ask Claude: "Check the Fusion 360 connection status"

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Tools

Tool	Description
fusion_execute	Run arbitrary Python scripts inside Fusion with full adsk.* API access
fusion_screenshot	Capture the active viewport as a base64 PNG

Example prompts

Create a 50 × 30 × 20 mm box centred on the origin
Make a 6 cm diameter sphere
Show me what's in the active design
Take an isometric screenshot
List all bodies and their volumes
Create a truncated icosahedron (soccer ball) 6 cm across

Security

The add-in binds to 127.0.0.1 only and requires a Bearer token on every request. The token is stored in ~/.fusion-mcp-secret — permissions are restricted to the current user only (mode 600 on macOS/Linux; NTFS ACL on Windows). Any request without a valid token receives a 401 Unauthorized response.

If you see a "WARNING: no secret file" message when the add-in starts, re-run the quickstart script or create the secret file manually (see step 2 above).

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Keeping the bridge up to date

The shim has two files that may need updating over time: the Fusion add-in and CLAUDE.md. The add-in's API surface is intentionally minimal (execute + screenshot), so it rarely needs changes. CLAUDE.md holds all the scripting knowledge and can be updated without touching any code.

After a Fusion update — paste into Claude

Read CLAUDE.md in this repo.

Then use fusion_execute to probe the running Fusion instance:
  print(adsk.core.Application.get().version)

Check whether any patterns documented in CLAUDE.md produce deprecation warnings
or errors against the current Fusion version. Report findings and update
CLAUDE.md only — no code changes needed.

When Autodesk ships native MCP support — paste into Claude

Autodesk has shipped native MCP support for Fusion 360.

1. Read .mcp.json, mcp-server/server.py, CLAUDE.md, and README.md in this repo.
2. List which of our two tools (fusion_execute, fusion_screenshot) are now
   available natively in Autodesk's MCP, and what their tool names/schemas are.
3. For tools now provided natively:
   - Update .mcp.json to point at Autodesk's MCP server
   - Remove mcp-server/ and fusion-addin/ directories
   - Remove scripts/quickstart-mac.sh
4. Update CLAUDE.md:
   - Remove workarounds for things now handled natively
   - Add any new native tool names or patterns worth knowing
   - Keep all Fusion API knowledge (units, revolve rules, TBrepM, etc.) —
     it is still valid regardless of the transport layer
5. Update README.md to reflect the simplified setup.

Do not delete CLAUDE.md. The scripting knowledge is transport-independent.

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Thread safety

Fusion's Python API must only be called on the main thread. The add-in uses Fusion's CustomEvent system to marshal every HTTP request from the background thread onto the main thread, then blocks with a threading.Event until the result is ready.

Port configuration

Default port is 7654. Override with an environment variable before launching Fusion 360:

# macOS/Linux
export FUSION_MCP_PORT=7655

# Windows
$env:FUSION_MCP_PORT = "7655"

Pass the same variable to the MCP server via env in your Claude config.

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Troubleshooting

"Cannot connect to Fusion 360"

• Ensure Fusion 360 is open with a design loaded
• Ensure the FusionMCPBridge add-in is running (Tools → Add-Ins)
• Check nothing else is using port 7654:
  • macOS/Linux: lsof -i :7654
  • Windows: netstat -ano | findstr 7654

"Unauthorized (401)"

• The secret in ~/.fusion-mcp-secret doesn't match what the add-in loaded at startup
• Re-run the quickstart script to regenerate a fresh shared secret, then restart both Fusion and Claude

"No active document"

• Open or create a Fusion design before using the tools

Add-in won't load

• Check Fusion's script console: Tools → Scripts and Add-Ins → Script Console
• The add-in folder must be named exactly FusionMCPBridge and contain both .py and .manifest files

MCP server not found by Claude

• Confirm the absolute path in your Claude settings file is correct
• Run python3 mcp-server/server.py manually to check for import errors

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License

MIT — see LICENSE.