What problem does it solve? Driving Onshape CAD through an MCP plugin fails silently without the right protocols: sketches drift, REMOVE extrudes cut into air, variables get wiped, and regen errors go unnoticed. This Skill encodes the render-first, entity-first, and regen-check workflows that keep parametric CAD builds correct. ## Core Features & Use Cases - Render-first verification: After every feature, call describe_part_studio, verify the feature tree and mass properties in text, then inspect the iso render and crop into suspicious regions. - Sketch discipline: Choose coordinate-first sketches for simple geometry or constraint-first sketches with the 14 constraint types for drawing transcription, and iterate with edit_sketch instead of rebuilding. - Entity-first targeting: Use list_entities to pick faces and edges by type, normal axis, and position before filleting, chamfering, or mating. - Parametric variables: Manage Variable Studios as separate elements, upsert variables by name, and avoid the known-broken variableCenter path. - FeatureScript escape hatch: Write custom features for threads, lofts, sweeps, and helical cuts when primitive tools cannot express the geometry. - Use Case: A user asks Claude to model a NEMA 17 motor mount from a drawing. The Skill walks through setting up a Variable Studio, building a constraint-first sketch, extruding with the correct direction, verifying via describe_part_studio, and reparametrizing to NEMA 23 by changing a few variable values. ## Quick Start Load this skill before building anything in Onshape so the MCP tool surface, unit conventions, and verification protocols are in context.
