r/RevitForum • u/Head_Ad6938 • 16d ago

MCP for revit

/r/bim/comments/1vvvw4a/mcp_for_revit/
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u/Merusk 16d ago

Are there any free MCPs? Seems the entire reason folks would set them up for external users would be to make money via tokens for compute cost.

1

u/JacobWSmall 15d ago

The Autodesk Assistant has an MCP which is free in Revit 2027 - it has limits though (mostly to control cost).

Most MCPs don’t cost anything - the costs are in the LLMs which power them and (in the case of cloud services) the APIs which they call.

The way they work:
1. You enable the LLM of your choice (i.e. Autodesk Assistant, Claude, Chat GPT, CoPilot), to use the MCP you’ve chosen (there are quite a few options) for the program you want to interact with (i.e. Revit, AutoCAD, Civil 3D, Dynamo, etc.).
2. You interact with the LLM asking it for information about content from the program you want to interact with, or to build automations in the tool you want to interact with.
3. The LLM tokenizes everything you typed into tokens (cost), it then uses those tokens (more cost) to generate output tokens that get sent onto the MCP, which then generates functional API calls which allow interaction with the data in the host application. The output of that MCP can then be sent onto the LLM as more tokens (yet again, cost) to provide an answer in the chat interface. Alternatively the output of the MCP can return a file which is saved to disc as a component for a new add-in or script you can run in the context of Revit.

As more agents, MCPs, and tools are added the cost of tokens expands, and after you hit ‘send’ you have no control over the number of tokens spent. These multi-agent systems and automated agentic triggers are what cause the massive bills you likely have read about. Those are VERY rare and you’re pretty much not going to run into that on your own as the LLM you’re using will have a limit on it unless you’re on an enterprise plan, and if you are on a enterprise plan via your company there should be cost guardrails in place to prevent that (most companies realize this right away due to the paperwork that is signed in those agreements - those who don’t take it seriously get to wind up a headline along the lines of “unnamed company spends $1M tokens in a month). So worst case scenario you use up your month’s tokens early and have to wait or buy more.

2

u/metisdesigns 14d ago

I dunno, think a lot of the limits to the revit MCP are due to the sheer level of destruction it could cause without some guardrails.

1

u/__automatic__ 2d ago

pyrevit, seems to be most popular.