cadloop Slicer MCP server

cadloop

<!-- mcp-name: io.github.richardofortune/cadloop-openscad --> <!-- mcp-name: io.github.richardofortune/cadloop-slicer -->

A closed loop from parametric source to G-code, with the verification step in the middle that neither the CAD tool nor the slicer can do.

Two MCP servers. A model writes OpenSCAD, compiles it, reads computed values back out, looks at a render, checks it fits the bed, slices it and pulls out the G-code, with every plate proven against the printable area. No GUI at any point.

The verify step in the middle is yours to write. cadloop makes everything around it cheap enough that you get to run it often; it cannot tell you whether the part works.

Every number in that walkthrough is real output. The failing wheel is a real measurement, not an illustration. How it's built and where each number comes from is in docs/walkthrough.

setup_printer   once, no arguments: which printer is this for
      |
  write .scad
      |
   check          syntax and references, about a second
      |
   echo           read computed values without rendering
      |
   preview        look at it
      |
   verify         does it actually work  <- yours; nothing here does it for you
      |
   measure        bounding box and volume
      |
 check_bed_fit    against the printer you set up
      |
  slice_model     -> .gcode.3mf
      |
 extract_gcode    -> .gcode

The ordering is the point. check and echo skip geometry evaluation entirely, so they cost a second against models where a full render takes minutes. Pay for the expensive steps only once the cheap ones pass.

Everything from the bed check down is also one call, make_printable, which renders, packs, slices and proves the result on the bed and reports what it did in a screen of text. See the worked example.

Install

pip install cadloop

The only dependency is mcp. Or from a checkout, which is what you want if you intend to run the worked example or the tests — the verify extra is shapely, needed by the example's own checker rather than by cadloop:

git clone https://github.com/richardofortune/cadloop
cd cadloop
pip install -e ".[verify]"

Needs OpenSCAD on PATH or at OPENSCAD_BIN, and for slicing, OrcaSlicer, Bambu Studio, ElegooSlicer or Creality Print. They share a CLI, so any of them works, and all four are auto-detected along with the profiles they ship.

No slicer is preferred over another here. setupprinter probes each one it finds and then proves the winner by slicing a 20mm cube with your profiles, so which one you get is decided by which one works on your machine rather than by the order of a list in this repository. Creality Print's CLI is broken headless on macOS today, and that is something this discovers rather than something it asserts, so it corrects itself when upstream ships a fix; see testing status below. SLICERBIN overrides the choice.

Configure

Copy mcp.json into your client's config and fix the paths. Both servers should point at the same workspace directory, which is the only place either one reads or writes.

The servers

Shortened. The full README is on GitHub.