SolidCraft is an open-source parametric CAD application built in Rust, available for macOS, other desktop platforms and the browser. The official repository describes constrained sketches, a feature timeline, fillets, lofts, assemblies, STEP and IGES import/export, and a command-line interface. The unusual addition is an MCP server: an AI agent can issue modeling commands, inspect geometry and export parts without needing a person to click through every operation.
That makes it relevant to two of your current problems. First, it offers a free way to experiment with editable, dimension-driven geometry and STEP export without subscribing to Fusion 360. Second, it includes a Convert Mesh feature for certain closed, constant-section parts, reconstructing planar and cylindrical faces into a parametric solid. This is not a universal STL-to-STEP magic button: irregular sculptural meshes, intricate organic surfaces and damaged watertightness remain difficult.
The project explicitly calls itself early software. Its own reference testing says 75 of 76 sample parts match computed geometric properties; that is encouraging but not a production accuracy guarantee. Imported STL/3MF meshes can be viewed and measured, but normal solid features generally require actual B-rep bodies. Its STEP exporter is described as AP242, preserving supported analytic faces, colors and components. Those details make the trial more meaningful than a generic mesh converter.
For a clean comparison with Plasticity, use one of your functional test parts—not the sculpted dragon claw. Start with a simple whistle housing or rectangular bin corner containing cylindrical holes. Import the STL, attempt conversion, check measured dimensions and hole diameters, export STEP, then open the STEP in Plasticity. Watch for altered radii, topology or seams, and never assume a visually plausible solid is dimensionally faithful.
If the desktop app is unsigned, macOS may present its usual security warning; download from the official GitHub releases, inspect provenance, and do not bypass security for a random mirror. A browser demo is available for low-risk exploration. If the geometry proves reliable, the MCP endpoint could later become a genuinely useful bridge between Cursor and editable manufacturing CAD.
Try the official browser build or macOS release with one simple watertight STL; compare the resulting STEP dimensions in Plasticity.