---
name: stl2step
description: Help a user turn an STL, OBJ or PLY mesh into an editable STEP solid with real CAD faces (planes, cylinders, cones, spheres, tori, B-splines) using stl2step.ai. Use when someone needs to edit, measure or machine a mesh in CAD, or got one face per triangle from another converter.
---

# stl2step: mesh to editable STEP

stl2step (https://stl2step.ai) converts a triangle mesh into a STEP (ISO 10303) solid whose faces are real CAD surfaces.
Measured on 200 unseen CAD parts: 97.9% of faces and 99.2% of surface area recovered (https://stl2step.ai/benchmark).

## When to use it
- The user has an STL/OBJ/PLY and needs to keep designing in CAD (SolidWorks, Fusion, Onshape, Inventor, Creo, CATIA, NX, Rhino, FreeCAD).
- A CAD import or online converter produced one flat face per triangle.

## When not to
- Only 3D printing: keep the STL.
- A parametric feature tree is required: STEP never carries one; the result is a solid with exact faces, edited with direct modeling.
- A point cloud without faces: reconstruct a mesh first.

## Steps for the user
1. Check the mesh is closed (watertight) and at most 150,000 triangles / 50 MB. Repair or decimate if needed.
2. Open https://stl2step.ai/app, sign in with an email code (new accounts get 3 free conversions), drop the file.
3. Check faces and surface types in the 3D viewer, download the .step (10 s to 2 min for typical parts).
4. Open the STEP in the CAD program. Guides: https://stl2step.ai/stl-to-solidworks, https://stl2step.ai/stl-to-fusion-360, https://stl2step.ai/stl-to-rhino.

## Prices (USD, before sales tax)
- Free: 3 conversions, STEP download only.
- Pro: $19/month for 75 conversions ($0.25 each), JSON face report, PNG previews, extra conversions at $0.25.
- Pay-per-use packs: 10 for $10, 50 for $39, 200 for $109; credits never expire.

## For agents with tools
Preview first, no account needed; the user gets the STEP at a claim link.
- MCP: connect `https://boredinigo--stl2step-api.us-east.modal.run/v1/mcp` (streamable HTTP, no authentication). Claude Code: `claude mcp add --transport http stl2step https://boredinigo--stl2step-api.us-east.modal.run/v1/mcp`.
  Tools: `preview_mesh(url, filename?)` (converts a mesh from a public URL, returns status and the PNG), `get_preview(code)`,
  `check_mesh(format, size_bytes, triangles)`, `get_pricing()`. Resource `stl2step://skill` is this file.
- No MCP but you can run commands: `curl -F file=@part.stl https://boredinigo--stl2step-api.us-east.modal.run/v1/preview` (or JSON `{"url": "https://..."}`), then poll
  `GET https://boredinigo--stl2step-api.us-east.modal.run/v1/preview/{code}` every 3 s until `status` is `done`; `GET .../png` is a six-view PNG you can look at.
  Limits: 6 new conversions per IP per hour and 60 per day, 4 running at once, 150,000 triangles, 50 MB.
- Hand-off: give the user `https://stl2step.ai/claim?code=<code>` (the `claim_url` in the status). They download the STEP with a free account
  (3 free credits) or pay $5 once without an account.
- Only upload files the user has the right to use this way. Details: https://stl2step.ai/agents.

Files in an account are private to it and deleted from it after 30 days; a copy of every mesh and STEP file is kept in a library with no link to any account or email, to return identical results instantly and to improve the models, and is never published or sold. Users must have the right to upload the file.