MCP server for Autodesk FlexSim (unofficial)

Run Autodesk FlexSim simulation models from Claude. Ask for a what-if run in plain language, and Claude opens your model without a window, sets its parameters, runs it, and reports the results.

Unofficial community project, not affiliated with or endorsed by Autodesk. Autodesk and FlexSim are trademarks of Autodesk, Inc., used here only to say which product this server works with. You need your own licensed copy of FlexSim, and its licence terms apply to everything you run through this server.

What you can ask

• "Find the FlexSim models in my Documents folder."

• "Run Line1.fsm for an 8-hour shift and show the performance measures."

• "Compare 3 and 4 operators on this model."

• "What's in the Schedule table of this model?"

• "List the objects in this model."

Each run is one replication. If your model has randomness, a difference between two single runs may just be chance, so run several seeds before drawing conclusions.

Related MCP server: FlexSim MCP Server

Tools

Each server handles one headless run at a time, with a time limit. The server stops FlexSim if it overruns or the call is cancelled.

Requirements

• Windows

• FlexSim, installed and licensed. Open it normally once to confirm it works.

• Node.js 20 or newer, for Options 1 and 3 below. Tested on Node.js 26. Older versions are covered by automated protocol tests only.

Install

Download flexsim-mcp.mcpb from the latest release, then choose one option. Using more than one in the same app can make the tools appear twice.

For Options 1 and 3, first unpack the server. A .mcpb file is a zip archive, so rename a copy to .zip and extract it to a permanent folder such as C:\Users\YOUR-NAME\.flexsim-mcp. Then check that server\index.mjs is inside that folder. Replace YOUR-NAME below with your Windows user name.

Option 1: Settings file (Claude Desktop)

1. In Claude Desktop, open Settings > Developer > Edit Config.

2. Add the flexsim entry to claude_desktop_config.json. If the file already has an mcpServers section, put the entry inside it:

   {
     "mcpServers": {
       "flexsim": {
         "command": "C:\\Program Files\\nodejs\\node.exe",
         "args": ["C:\\Users\\YOUR-NAME\\.flexsim-mcp\\server\\index.mjs"],
         "env": { "FLEXSIM_TIMEOUT_SECONDS": "600" }
       }
     }
   }

3. Quit Claude completely and reopen it.

Use the full path to node.exe, because desktop apps don't always inherit your terminal's PATH.

Option 2: Claude Desktop extension

Not yet verified by this project. In Claude Desktop, open Settings > Extensions > Advanced settings > Install Extension and choose the .mcpb file. You can then set the FlexSim path and time limit in the extension's settings. Reports on how this goes are welcome.

Option 3: Claude Code CLI

claude mcp add flexsim --scope user -- "C:\Program Files\nodejs\node.exe" "C:\Users\YOUR-NAME\.flexsim-mcp\server\index.mjs"

Check it works

Ask Claude: "Run the FlexSim smoke test." You should get smoke_test: passed within about a minute. If not, see Troubleshooting.

Long runs

Claude apps stop waiting for a single call after a limit of their own, and when they cancel a call, FlexSim is stopped too. In Claude Desktop's Code tab, that limit was measured somewhere between 50 and 90 seconds. Raising timeout_seconds doesn't change it, because that setting only controls when the server itself stops FlexSim.

So long simulations run in the background. flexsim_start_run returns straight away, and flexsim_get_run collects the results across as many calls as it takes, so just ask Claude to run the model and tell it the run may be long. A 94-second run was tested this way through the Code tab. A few things to know:

• FlexSim runs one at a time. While a background run is going, other FlexSim calls are refused with a message saying so, and further flexsim_start_run calls wait in line.

• Background runs have a default limit of one hour, and up to two hours with timeout_seconds.

• A run belongs to its server, which usually means one Claude session. Quitting Claude stops FlexSim and loses the run, so results aren't kept.

Settings

Leave FLEXSIM_EXE unset and the server moves to a new FlexSim version automatically when you install one. If it's set to a path that doesn't exist, the server uses the newest install instead; check exe_in_use and exe_source in the smoke test output.

Tested with

Security

FlexScript has full access to your computer, and this server adds no sandbox. A script can read and write files with your Windows permissions, and opening a model can run code stored in it. Review what Claude proposes to run if your models or data are sensitive. See SECURITY.md.

Documentation

• Troubleshooting

• Architecture and FlexSim behaviour notes

• Roadmap

• Contributing

• Changelog

Licence

MIT. This licence covers this server only, not FlexSim. The release file includes the licences of the code bundled into it.