MCP for Mechanical Engineers

Mechanical engineering is the discipline where AI connectors are simultaneously the most developed and the most oversold. There are more MCP servers for CAD than for most design tools, several advertise eighty or ninety “tools,” and almost none of the write-ups mention the two licence restrictions that decide whether you can legally use them at all.

This is the third article in our series on MCP servers, discipline by discipline, following the one on industrial design. This one is for people who produce manufacturing data.

Start with the licences, because they disqualify things

Two of the most widely recommended free CAD options cannot legally be used for commercial work, and this is rarely stated in the roundups.

Onshape‘s free plan makes every document public. Not private with a shareable link — public, and discoverable. For learning and hobby projects that is a fair trade. For anything under NDA, anything patentable, or any client work at all, the free tier is disqualifying regardless of how good the tooling is.

Fusion 360‘s free personal licence is non-commercial, and also caps active documents while removing generative design and most CAM post-processors. People routinely discover this after building a workflow on it.

FreeCAD is the only genuinely free option here with no commercial restriction whatsoever. That fact alone should shape which connector you invest time in.

Onshape: the only official server in CAD

Onshape Labs ships a FeatureScript MCP server, and unlike everything else in this article it is a vendor product. It lets engineers create custom Onshape features by describing them in natural language instead of writing FeatureScript by hand.

Separately there are connectors that wrap the Onshape REST API into a set of semantic tools, handling authentication, caching and rate limits so the assistant works with meaningful operations rather than raw endpoints.

This is the strongest official story in CAD, and it is genuinely strange how little attention it gets.

Where it falls short: the official server is aimed at FeatureScript authoring — extending Onshape — more than at everyday modelling. It is cloud-only by nature, so an offline requirement or an IP policy that forbids cloud CAD rules it out entirely. API rate limits are a real constraint on heavy automated use.

SolidWorks: crowded, capable, and Windows-only

Dassault has not shipped an MCP server. What exists is a surprisingly active set of community projects for SolidWorks, and they differ from each other in ways that matter more than their feature lists suggest.

Between them they cover part and assembly creation, sketching, extrusion, running simulations and exporting to STEP, IGES, STL and PDF. One Python project advertises 90+ tools across modelling, drawings, export and macros; a Node.js one advertises 88 tools with a COM bridge.

Ignore those numbers. Tool count is a packaging decision, not a capability measure — one project’s single flexible tool is another’s twelve narrow ones.

The more interesting difference is architectural. One project, SolidPilot, has the assistant produce intent at the feature level — “put a hole in the top face” — expressed as a CAD-neutral Feature Graph intermediate representation, which a deterministic compiler then lowers into ordered SolidWorks operations. That is a meaningfully better design than letting a language model emit API calls directly, because the deterministic layer is where correctness can actually be enforced. It targets SolidWorks 2026.

Where it falls short: these drive SolidWorks through COM, which means Windows only — no exceptions. There is no vendor backing, so a SolidWorks service pack can break a connector with nobody obliged to fix it. And with this many competing projects, none canonical, evaluating them is itself a real time cost. Check the commit history before you invest.

FreeCAD: free in every sense, and fragmented

FreeCAD has the most MCP implementations of any tool in this article, which is both a strength and the problem. At least five are actively published and none is official, because there is no official one.

Capabilities across them include geometry creation, boolean operations, document management and running custom scripts, with some going further into containerised headless execution and vision-based analysis of the model.

Where it falls short: choosing costs you an afternoon. Some are Node-based, some Python, with different prerequisites. FreeCAD’s own API has shifted between versions, so a server built against one release may not work with yours. The long-standing topological naming problem also means edits early in a model can break later features — an assistant making rapid changes can hit this faster than a human would.

KiCad: the electronics half nobody covers

Most mechanical work eventually touches a PCB, and this is better served than you would expect.

Several KiCad MCP implementations exist. They handle project management, schematic analysis, layout operations, design rule checking and export, and the more developed ones add custom symbol and footprint generation, personal library management, JLCPCB parts catalogue integration and Freerouting for automatic routing.

Design rule checking is the standout. Asking an assistant to run DRC and explain what each violation means is a genuine use of the technology — it is reading and interpreting deterministic output rather than generating geometry and hoping.

Where it falls short: auto-routing has always been a compromise, and an assistant invoking it does not change that. Component selection is also a judgement call involving availability, lifecycle and cost, none of which the connector knows about. Verify every part choice against real stock.

What this is genuinely good for

Being specific about where the gain is real:

• Boilerplate and repetition: the strongest fit. Generating families of similar parts, batch exports, renaming and reorganising, macro-style work you would otherwise script by hand.
• Reading and explaining: interrogating an existing model, summarising a DRC report, explaining why a feature failed. Low risk, immediately useful.
• Custom feature authoring: Onshape’s FeatureScript server is the clearest example — describing a feature beats writing it from scratch.
• Tolerancing, GD&T and manufacturing intent: no. Nothing here understands fits, draft angles, material behaviour or what your supplier can actually hold. Confident wrong output is more expensive in this part of the process than anywhere else in design.

There is a fair criticism that AI in CAD makes modelling faster without addressing the actual bottleneck, which in most engineering organisations is review and decision-making rather than modelling speed. If your projects are slow because sign-off is slow, none of this helps.

Before you connect anything

These servers work by executing code inside your CAD application — Python in FreeCAD and Fusion, COM calls into SolidWorks. That is the mechanism, and it is the risk.

• Use version control or PDM, not undo. An assistant that can create features can delete them, and in a parametric model a bad edit propagates.
• Check what leaves your machine. Engineering work is routinely under NDA. Local servers generally keep data local, but confirm it for the specific project rather than assuming.
• Never let generated geometry reach a supplier unreviewed. Treat output as a draft from someone competent but unfamiliar with your standards.

Frequently asked questions

Is there an official SolidWorks MCP server?

No. Every SolidWorks connector is a community project. Onshape is currently the only major CAD vendor shipping an official MCP server.

Can I use these on a Mac?

Not for SolidWorks — those connectors use COM and are Windows-only. FreeCAD and Onshape connectors are cross-platform, and Onshape runs in a browser, so a Mac-based workflow points toward those.

Which free CAD can I legally use commercially?

FreeCAD. It is open source with no commercial restriction. Onshape’s free plan makes documents public and Fusion 360’s free personal licence forbids commercial use, so despite being the two most-recommended free options, neither qualifies.

Does an MCP server understand tolerances and GD&T?

No. It can place a dimension you describe, but it has no model of fits, manufacturing capability or material behaviour. Every tolerance decision remains an engineering judgement.

Are servers advertising 90+ tools better?

Not necessarily. Tool count reflects how an author chose to slice the API, not capability. A project with fewer, well-designed tools and active maintenance is a better bet than a large surface abandoned six months ago.

Sources and when we checked them

All claims verified in August 2026. Community projects in this category change status without notice, and licence terms change too — check the vendor’s own page before committing.

• Onshape — How Onshape Labs FeatureScript MCP Server enables text-to-code-to-CAD
• eyfel/mcp-server-solidworks (SolidPilot) — the Feature Graph IR approach described above
• andrewbartels1/SolidworksMCP-python
• neka-nat/freecad-mcp and bonninr/freecad_mcp
• lamaalrajih/kicad-mcp and mixelpixx/KiCAD-MCP-Server
• Autodesk Fusion MCP: Faster CAD, Same Bottleneck

If you are weighing a move away from SolidWorks entirely, the SolidWorks alternatives guide covers the same tools on price and licensing rather than AI tooling.

MCP is worth considering for repetitive CAD work, model interrogation, report explanation and custom feature authoring, especially when you can review every change. Skip it if you need unattended engineering judgement, cloud-hosting is prohibited, or your real bottleneck is review and sign-off rather than modelling.

Keep reading

• MCP servers for CAD
• MCP for industrial designers

Frequently asked questions