onshape-mcp (mbvjdev)

onshape-mcp is a local MCP server that gives the Hermes Agent practical, rate-limited tools for creating and inspecting Onshape CAD. It turns model requests such as creating a 100 mm disc with a 30 mm center hole into semantic CAD operations, while handling Onshape API authentication, rate limiting, caching, FeatureScript operations, and the difficult parts of the REST API.

Its tools cover documents, parts and features, sketching, and 3D operations: search, list, create, and inspect documents and Part Studios; inspect parts, feature trees, and individual features; create sketches on standard planes with circles, lines, and rectangles; extrude, revolve, fillet, and chamfer; and export STL files and retrieve shaded thumbnails. All dimensional tool inputs use meters, because that is Onshape's API unit.

The README explains why an MCP layer exists: the raw Onshape API relies on internal btType values and transient IDs, naive clients hit account-level rate limits quickly, some operations use FeatureScript because their REST variants are fragile, and a malformed feature request can leave a Part Studio in a bad state. Credentials stay in the user's local Hermes environment file and are passed only to the MCP subprocess; the repo contains no API keys, personal Hermes configuration, or Onshape documents.