# What is an MCP server?

- Link: https://vibecad.nl/en/what-is-an-mcp-server/
- Published: 2026-10-22T21:44:45+02:00
- Author: Marijn van den Heuvel \+ AI

_This is the English reading version of the Dutch explainer [Wat is een MCP-server?](https://vibecad.nl/2026/10/21/wat-is-een-mcp-server/)._

You come across the abbreviation more and more, including in reports about CAD. 
MCP is the agreement that lets an AI model operate tools. Below is what it is, what
it does in CAD, and where it stops.

## What it literally is

MCP stands for Model Context Protocol. It is an agreement between two parties: on
one side the AI model you use, on the other a program that can do something. That
agreement describes which actions the program offers and how the model has to call
them. A program that follows that agreement is called an MCP server.

Without such an agreement, every combination of model and program has to be built
separately. With it, that is not needed: every model that knows the agreement can
talk to every server. For you that means you are no longer tied to one vendor’s 
assistant, although not every vendor sticks to that.

## What an MCP server does in CAD

In CAD the server is the tool between the model and your drawing program. Such a
server can do two things. Watching along: the model reads your document, your dimensions,
your properties and the build-up of your model. Or joining in: the model makes sketches
and features, puts assemblies together, measures and exports to STEP or STL. Which
of the two it is differs per program. AutoCAD, for instance, is read-only in its
server, while in Fusion and Onshape you can really model.

## What it is not

An MCP server is not AI. It cannot think anything up and cannot solve anything; 
it only offers the actions and carries out what the model asks. That is why the 
result depends on the model you put on it, and not on the server. Put a weak model
on it and you get weak work, even if the CAD program is the same.

Nor is it a cloud service. Usually the server simply runs on your computer, next
to your CAD program. Sometimes that program has to be open, sometimes a separate
server or plugin is started alongside it.

## Why you see it more and more

A year ago hardly any CAD program had such a server. Now every large vendor has 
one, or announces one, and the open-source projects have one too. That says something
about the direction: not a program with an AI button in it, but a program that a
model can operate from outside. So the question is no longer which program you use,
but which model you put on it. Which programs already have a server is in the [overview of CAD programs with MCP](https://vibecad.nl/en/which-cad-programs-support-mcp-in-2026/).

Which model suits what task is on [AI models for vibecadding](https://vibecad.nl/en/ai-models/).

The agreement itself is described at [modelcontextprotocol.io](https://modelcontextprotocol.io/),
with the specification and the list of clients and servers.