Give it an STL of a mechanical part and get back an exact STEP solid plus an editable CadQuery or OpenSCAD script with named parameters.
This page shows precomputed results on real 3D printer parts, so it loads instantly. To run it on your own STL: pip install mesh2cad then mesh2cad convert part.stl -o part.step --cadquery part.py. Source, docs and the MCP server: github.com/emirmrkaljevic/mesh2cad.
Honest limits: it works on CAD-exported meshes of prismatic parts (planes, cylinders, cones, spheres, extrusions and simple booleans). Organic shapes, sculpts and noisy scans are refused instead of faked. Complex outlines such as belt teeth come out as polygon points, not as named parameters.
Example STLs are unmodified printed parts from prusa3d/Original-Prusa-i3 (GPL-3.0), used here for demonstration. Orange is the input mesh, blue is the reconstructed STEP solid. mesh2cad itself is MIT licensed.