SolidWorks

SolidWorks MCP

Let an AI agent (Claude, or any other MCP client) model real parametric parts and assemblies in your own SolidWorks — and check its own work. Every modelling call returns the measured volume, mass and bounding box, so the agent can compare the result with the spec and correct itself instead of guessing that it "looks about right".

Built by the tools themselves: a mounting bracket (every step checked against a hand calculation), an M10 bolt with a real thread, a revolved + shelled vase, a swept pipe, a lofted + shelled horn.

Why this server

• It verifies, not just generates. Features report measured geometry; dimensions and mates are measured back after the rebuild.
• Fully defined sketches. Every sketch is constrained the way a designer would: dimensions from the origin, relations only where the geometry is exactly horizontal, vertical or on the origin. Tools return their dimensions by role (width@Sketch1), so the part stays editable, in SolidWorks or through the agent.
• Real CAD, not just primitives. Extrude, revolve, sweep, loft and splines; holes, counterbores, slots and pockets on any face; rounded polygon corners; ISO holes from the Hole Wizard; real ISO metric threads; fillets, chamfers, shells, patterns, mirrors, ribs, equations and materials. Assemblies with mates and interference checks. STEP/STL/3MF export and screenshots. Engraved and embossed text. Work on existing parts: list, delete, suppress and reorder features; read, extrude and cut a person's sketches; import STEP. Colours per part or component. Joints with concentric and angle mates, checked over their range. Printability checks and dimensioned drawings. Planes at any offset or angle. Several bodies per part, combined and split. Variable fillets and full rounds. Free sketches with tangent arcs and splines. 88 tools in total.
• It fails loud. A call that cannot do what was asked returns {ok: false, error} with the cause, never silently wrong geometry.
• A fixed, typed tool surface. There is no "run arbitrary code" tool; the agent can only do what the tools allow.
• Tested against real SolidWorks. 733 tests; each feature's integration test compares the result with a hand calculation.
• Local. It talks to your running SolidWorks over COM; the server itself makes no network calls.

Quickstart

1. Install uv.
2. Start SolidWorks and leave it open (the server attaches to the running instance — it does not launch one).
3. Register the server with your MCP client.

Claude Code:

   claude mcp add solidworks -- uvx solidworks-mcp

Claude Desktop (claude_desktop_config.json) or any other client:

   {

"mcpServers": { "solidworks": { "command": "uvx", "args": ["solidworks-mcp"] } } }

It is also listed in the official MCP Registry as io.github.hjbaard/solidworks-mcp.

1. Ask for a part, for example:

Design a 100 × 80 × 8 mm mounting plate with a Ø16 mm centre bore, four

counterbored M5 holes 12 mm from the corners and R5 corners. Check the

volume against your own calculation, then export a fine STL.

Guidelines for agents

The server hands every MCP client short modelling guidelines when it connects (conventions, verify each step, known pitfalls). The full guide is the resource solidworks://guide: recipes for holes, ribs, threads and assemblies, 3D-print advice, and how to reverse-engineer a part from a mesh (STL/3MF). The same text is in src/solidworks_mcp/guide.md.

Requirements and compatibility

• Windows, with SolidWorks installed, licensed and running.
• Python 3.11+ (uv fetches one if needed).
• A Y-up part template, SolidWorks' standard. Since SOLIDWORKS 2025 new parts can also be Z-up; the tools build in the Y-up frame and refuse a Z-up part with a message that says so. Choosing Y-up in the New Document dialog is not used for parts made through the API: make a Y-up part, save it as a .prtdot, and set that file as the part template under Tools > Options > System Options > Default Templates.
• Tested on SOLIDWORKS 2026 (3DEXPERIENCE R2026x). The API calls it uses exist since SOLIDWORKS 2020 SP2, so 2020–2025 should work, but that is untested. To check your installation, run this with SolidWorks open:

  uvx solidworks-mcp --selftest

It builds a few small parts, compares each with a hand calculation and closes them unsaved. Please paste its output in a compatibility report, whether it worked or not.

Status: early (0.x). It works end-to-end, but tool names and conventions may still change. See CHANGELOG.md.

Troubleshooting

• Start with the selftest: uvx solidworks-mcp --selftest shows your SolidWorks release, language and templates, and which tool areas work. Add its output to a bug report.
• "No running SolidWorks found" / connection fails — SolidWorks must be *running* before you start the server or run a script; it attaches to the active instance via GetActiveObject and does not launch one.
• First call is slow or `EnsureModule` errors — the first COM call generates the makepy typelib wrappers under your temp gen_py folder. Let it finish; if it gets into a bad state, delete the gen_py cache and retry. Early binding is mandatory on this build (see Architecture).
• A feature returns `{ok: false, error: ...}` — that is by design: every tool fails loud with a readable message rather than silently producing wrong geometry. Read the message; it names the likely cause.
• Only tested against SOLIDWORKS 2026 (3DEXPERIENCE R2026x). On other builds the verified enum values or method signatures may differ — re-run scripts/introspect_api.py to inspect your installed typelib.

Development

Clone the repository, then install it editable into a venv:

python -m venv .venv

.\.venv\Scripts\python.exe -m pip install -e .[dev]

To run the MCP server from this checkout instead of via uvx, point your client at the venv's Python:

{

"mcpServers": { "solidworks": { "command": "C:\\path\\to\\SolidWorks-MCP\\.venv\\Scripts\\python.exe", "args": ["-m", "solidworks_mcp.server"] } } }

Run the verification scripts

With SolidWorks open:

.\.venv\Scripts\python.exe scripts\probe_connection.py     # M0

.\.venv\Scripts\python.exe scripts\m1_block.py # M1 .\.venv\Scripts\python.exe scripts\m2_parametric.py # M2 .\.venv\Scripts\python.exe scripts\test_mcp_server.py # M3 (full MCP loop over stdio) .\.venv\Scripts\python.exe scripts\m5_demo_bracket.py # M5 (3D-print bracket, every step verified)

scripts/introspect_api.py regenerates/inspects the installed typelib and prints verified enum values — run it if SolidWorks is upgraded and signatures change.

Tests

.\.venv\Scripts\python.exe -m pytest                 # all tests

.\.venv\Scripts\python.exe -m pytest -m "not solidworks" # fast unit layer, no SolidWorks

Two layers: pure unit tests (units, selector/direction parsing, polygon cleaning, the component-placement maths, and that every MCP tool forwards its arguments to the right session method) run anywhere; integration tests (solidworks marker) drive a running SolidWorks and verify each feature's volume — or each component's placement — against a hand calc. They auto-skip if SolidWorks isn't reachable.

Tools

The server speaks MCP over stdio.

Part tools

| combine_bodies(operation, main, tools, name) | Add, su