PartMode MCP
Hosted MCP server for the PartMode browser CAD that lets an agent edit parametric parts, assemblies and drawings
- 505 ★ on the repository
- Last commit
- AGPL-3.0
Extended access
Why this level
- The agent calls an external service and edits a project, and every commit is bound to the document revision
- Commands and replies pass through the PartMode server without end-to-end encryption
Install
- Works in
Manual install
codex mcp add partmode --url https://partmode.com/mcp --bearer-token-env-var PARTMODE_AGENT_KEYThe key is created on the Agent access page of a PartMode account and kept in the environment variable the client reads.
Access and checks
How we reviewExtended accessThe tool runs code or makes network calls and only reads external data.
- The agent calls an external service and edits a project, and every commit is bound to the document revision
- Commands and replies pass through the PartMode server without end-to-end encryption
This is third-party code. Review the repository files before installing.
What it does
PartMode is a browser-based mechanical CAD built on OpenCascade WebAssembly. An agent connects to it through a hosted MCP server and works on the same document as a person: sketches with dimensions and expressions, feature history, assemblies with mates, drawings. An exact B-rep kernel computes the geometry, so a failed rebuild reaches the agent as an error. In a browser session you keep the project open in a PartMode tab and approve the agent's access to the project once. The agent reads state through cad_inspect and cad_query, prepares a change in cad_preview and commits it with cad_commit only if the document revision has not changed. You can reject the connection, pause the session or revoke the key at any time. For work without an open tab there is a headless mode. A key with a separate grant opens a project on the PartMode server, and the partmode_headless_export_step tool exports the model to STEP. The server exposes 15 tools in total, and cad_capabilities returns the operations a given build supports.
Who it is for. For mechanical engineers and developers who hand parametric part and assembly modeling to an agent and take finished STEP files for other CAD systems.
Good fit when
- You need to change a dimension or expression in a parametric model and rebuild the geometry while you watch the result in the tab
- You want to assemble parts with mates and check mass, center of mass and inertia tensor from materials
- You need an exact STEP export on a schedule or from a script, without an open browser
- You want to see every agent change in a preview before it reaches the project
Not a fit when
- You need an offline mode: there is no command queue, and the relay keeps commands only in process memory
- You need engineering simulation, CAM or native DWG: PartMode does not support them yet
- You need full DXF output: the DXF export covers a restricted R12 subset
- You work in SolidWorks, FreeCAD or AutoCAD: PartMode drives only its own projects
Example request
Connect to my PartMode project, increase the bracket thickness to 6 mm, show the preview and commit the change after I confirmMCP
- Transport
- http
- Authentication
- API key
Environment variables
PARTMODE_AGENT_KEYrequired, secret- Revocable agent key from a PartMode account, sent by the client as a bearer token
Limitations
- A PartMode account and a revocable agent key are required. The key alone grants no CAD authority: rights come from an approved browser session or from the headless grant, which is set when the key is created and cannot be added later.
- The relay between the agent and the tab has no end-to-end encryption. The project stays in the browser, and commands and replies travel over HTTPS through the server.
- An active headless session lasts at most one hour and does not survive a service restart. Committed documents are kept on the server until the account is deleted. There is no per-project delete control yet, and the limit is 32 projects.
- The cad_artifact, cad_ui and cad_events tools work only in a browser session, and in headless mode STEP is the only artifact.
How to disable. Revoke the key on the Agent access page of your PartMode account: key authentication stops immediately and live headless sessions close. Then remove the partmode entry from your agent's MCP settings.
FAQ
How do I connect PartMode to Codex?
Create a key on the Agent access page of your PartMode account, store it in the PARTMODE_AGENT_KEY variable and run `codex mcp add partmode --url https://partmode.com/mcp --bearer-token-env-var PARTMODE_AGENT_KEY`. The server shows up for the agent after a session restart.
How is a PartMode browser session different from headless?
In a browser session the project stays in your browser, and you approve the agent's connection in the tab. In headless mode the agent works on a copy of the project on the PartMode server, with no open tab and no approval.
How do I export a PartMode model to STEP through an agent?
Open a headless session with partmode_headless_open and a stable projectId, make the edits, then call partmode_headless_export_step. The key for this has to be created with the headless grant from the start.
Can I run PartMode myself?
Yes, the AGPL v3 license allows it. It needs Node.js 22.13 or newer: clone the repository, run `npm ci`, `npm run build` and `npm start`, then open http://127.0.0.1:4401. Local browser CAD works without an account.
What does PartMode store on the server while an agent works?
In a browser session the server does not save the project. In headless mode the server keeps the project ID and name, the revision, the full document JSON, its hash and timestamps.
Discussion
No questions or reviews yet.
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Comparison with similar tools
Entries that share the main search query, and how they differ.
| Entry | Official | Authentication | Repository stars | Main difference |
|---|---|---|---|---|
| PartMode (this entry) | yes | API key | 505 | |
| FreeCAD MCP | no | not required | 3,108 | drives desktop FreeCAD on your machine, while PartMode runs in the browser with approved changes |
| SolidWorks MCP in TypeScript | no | not required | 245 | drives an installed SolidWorks on Windows, while PartMode keeps CAD in the browser |
| CAD-MCP Server | no | not required | 653 | draws in AutoCAD, GstarCAD and ZWCAD, while PartMode models parametric solids and assemblies |
README in short
The repository page walks through capabilities by area: parts, assemblies, drawings, exchange formats and geometry inspection. Next come a diagram of the two agent authority paths, a self-hosting recipe with npm and an architecture map. The end covers contributor rules and the smoke checks to run after changes.