diff_step
Compare two STEP files. Returns deltas: volume, surface area, dimensions, face/edge/body counts. Comparison minus baseline.
LABSCO SUMMARY
Manufacturability questions answered by a geometry kernel, with the model never leaving the machine.
The measurements come from Open CASCADE rather than from a model's impression of the shape, which is the difference between a design review and a guess. It is read-only by construction — it will report the wall thickness face by face and flag the undercut, and leave changing it to you.
What it is
An MCP server that reads STEP files with the Open CASCADE kernel on your own machine. It answers geometry questions with measurements rather than estimates — bounding box and volume, face and edge queries, thickness and draft, clearance between entity sets — and it never modifies the model. No CAD licence and no cloud upload.
What you get
- inspect_step — the compact overview to start from: dimensions, bounding box, body, face and edge counts, validity and watertight status, with optional bodies, quality, PMI, inertia and topology sections
- find_faces — faces by type, area, radius, normal, quality or body, returning IDs, surface types, areas, radii, diameters, axes and normals for use in the measurement tools
- find_edges — edges by curve type, length, radius or dihedral angle, returning IDs, lengths, radii and diameters
- measure_distance — distance between two sets of entities, such as the clearance between holes and walls, with a minimum summary for the closest pair
- measure_thickness — wall thickness across faces by ray-grid sampling, reported as min, max and average per face
- measure_draft — draft angles relative to a pull direction, with the normal and an undercut flag per face
- measure_geometry — ray tests, point analysis, cross-sections and edge continuity, selected by measurement type
- diff_step — two STEP files compared: deltas in volume, surface area, dimensions and face, edge and body counts
Requirements
Node.js 24 or newer and a STEP file exported from SolidWorks, FreeCAD, Fusion 360, CATIA or any other CAD system. Clients run npx -y cad-mcp-server over stdio. The OCCT kernel is bundled, so there is no CAD software, licence, Docker or cloud API involved, and the files stay on your machine.
Setup effort
One command — npx -y cad-mcp-server
USE CASES
01
Reviewing a part before tooling
Get the overview, then check wall thickness and draft angles against the pull direction and flag undercuts.
02
Checking clearances
Find the holes and the walls as entity sets and measure the closest pair between them.
03
Working out which holes are which
Query the cylindrical faces by radius and axis, then run a ray test to tell blind from through.
04
Comparing two revisions
Diff the STEP files and read the deltas in volume, dimensions and feature counts.
05
Finding the smallest fillet
Query the edges by curve type and radius and read the minimum.
8 tools
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
find_edges
Find edges by curve type, length, radius, or dihedral angle. Returns IDs, curve types, lengths, radii, diameters. Use returned IDs in measure_distance or measure_geometry.
find_faces
Find faces by type, area, radius, normal, quality, or body. Returns IDs, surface types, areas, radii, diameters, axes, normals. Use returned IDs in measure_distance, measure_thickness, measure_draft, or measure_geometry.
inspect_step
Use this FIRST for a compact model overview: dimensions, bounding box, body/face/edge counts, validity, watertight status. Use include[] for bodies, quality, pmi, inertia, or topology detail.
measure_distance
Measure distance between entity sets. Pass sources[] and targets[] for set-based measurement (e.g. clearance between holes and walls). Use summary="minimum" for the closest pair only.
measure_draft
Measure draft angles of faces relative to a pull direction. Returns draft_angle_deg, normal, and undercut flag per face. Positive = good for ejection; negative = undercut.
measure_geometry
Ray tests, point analysis, cross-sections, and edge continuity. measurement_type selects the operation: ray, ray_grid, point_analysis, section, or continuity.
measure_thickness
Measure wall thickness across faces via ray grid sampling. Returns min/max/avg thickness per face. Use direction_mode="normal" (default) or direction_mode="axis".
BEFORE YOU INSTALL
What to know first
Tools you get
8 tools when we connected.
Requires
- npx on PATH
- Node.js 24+
CONTEXT COST
Light Standing cost
Rated by the size of the 8 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Connect your client
Add the block to your client, or run the command directly.
Server setup
Configuration file
JSON
{
"mcpServers": {
"cad-mcp-server": {
"command": "npx",
"args": [
"-y",
"cad-mcp-server"
]
}
}
}npx
TERMINAL
npx -y cad-mcp-server
