After seeing a video a few months ago demonstrating how a proprietary CAM solution uses machine learning and large language models to automatically generate CNC instructions, and successfully testing it on a real CNC, I began wondering if the same could be achieved with free software. I still do not know the answer, but I may be getting closer to finding out. Two weeks ago, I came across the video "I Connected Claude AI to FreeCAD (And It Models Parts Like an Engineer)" by Make Form, which introduced me to the FreeCAD MCP project. Even though the video creator apparently believes it is acceptable to download and run random binaries from the Internet on a local machine (his setup uses UCX), I do not. I would probably have left the project alone entirely if I had not noticed that all of its dependencies are already available in Debian. This significantly boosted my motivation, so I set out to test it using packages built from source on Debian rather than relying on untrusted binaries.
The first hurdle was that the MCP SDK for Python was not present on my Debian Forky test machine. I initially believed it was missing from Debian altogether, but it has been available in Debian Unstable for about a month and is only absent from Forky because some automated tests fail on architectures like riscv64 and s390. Fortunately, backporting it was straightforward using `apt-get source -b python3-mcp`. The next hurdle involved an outdated version of the Validators Python library. Since I am a member of Debian's Python team, which maintains this package, updating it to a sufficient version for FreeCAD MCP was relatively easy. I could not upgrade to the latest upstream release due to a new dependency on an Ethereum-related library, so I settled on a 2024 version.
With those dependencies in place, I proceeded to create a Debian package for FreeCAD MCP. I had previously submitted a request for packaging of FreeCAD MCP to gauge interest while deciding whether to prioritize maintaining it myself. Because salsa.debian.org blocks access from Tor users like myself, I published my draft packaging scripts in a Git repository on Codeberg as the Debian FreeCAD MCP project and got it working with the FreeCAD 1.1 version in Forky. I initially struggled with the button controls for the MCP feature, which led me to submit a pull request titled "Fixed startup sync of checkable toolbar buttons" proposing a fix. Once this confusion was resolved and the MCP setup was enabled via the GUI, I was able to run FreeCAD completely headless using `xvfb-run` on a machine without an X server to generate models. I am using a private LLM service running the Debian package of llama.cpp with the Qwen 3.6 model downloaded from Hugging Face, configured with a maximum context window of 105k tokens. I also tested the Bonsai model on my test laptop; initially, its context window was too small (8k and 16k could not accommodate the FreeCAD MCP instructions), but even after increasing it to 32k, it proved useless for generating FreeCAD models so far. I've used Claw Code, Aider and Open Code with my server so far, and for this test I ended up with OpenCode because it was easy to set up to use an MCP. Because none of my LLM services are set up to be multimodal (capable of processing both text and images in this case), I configured the MCP to return only textual feedback from FreeCAD. I am unsure if this is a major limitation, though I suspect it might be.
My testing experience remains limited, with no clear successes yet. Part of the issue likely stems from my ability to provide effective instructions for modeling 3D objects (I am relatively new to FreeCAD, English is not my first language, and I lack a precise vocabulary for describing construction features to an LLM). Nevertheless, the LLM has demonstrated the capacity to create 3D models in FreeCAD. In one of my first tests, I asked it to generate a cube and then produce CAM/G-code instructions for a CNC machine. It did output G-code (which remains untested), but I was surprised to find that it bypassed FreeCAD's built-in CAM module entirely and instead generated an external Python script to produce the code. This was not quite what I intended, though my instructions were probably unclear. The Qwen model with OpenCode seems to strongly prefer programming directly; it frequently executes Python snippets inside FreeCAD to achieve its goals rather than using the standard sketch-and-extrude workflow I am accustomed to. In another test, I asked the LLM to create a parameterized pipe assembly to see which of FreeCAD's parametric tools it would choose, but found no evidence of traditional parametric features in the output. When prompted, the LLM explained that the parameters were embedded directly in the Python script used to generate the model, rather than in native FreeCAD features. With more explicit instructions, it eventually created a FreeCAD spreadsheet to manage the parameters. The resulting model looked much closer to my expectations and could have been useful with further refinement. My so far last experiment was less successful: I asked it to design a pipe clamp, but the LLM repeatedly failed to position the clamping screws in a way that would actually secure the brackets around the pipe. It is unclear whether this limitation lies with the model, my prompt, or other factors.
Based on my testing so far, I am uncertain whether FreeCAD MCP is merely a fun toy or a genuinely useful tool. I will only commit time to maintaining it in Debian if it proves to be practically valuable. I would welcome feedback from anyone who has experience with the project, preferably via the original request-for-packaging mailing list thread. Alternatively, I am available in the FreeCAD and Debian AI IRC channels for further discussion.
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