Conciseness

The body is dense and operational with no padding or explanations of known concepts — every line carries a build contract or decision rule. It falls short of a 5 only because full call syntax like "cad.edit` `action=\"add_part\"" is repeated verbatim many times (Loop, Python Cell Contract, Deleting sections) where a once-defined shorthand would trim tokens.

Actionability

Guidance is fully executable: concrete dispatch rules ("The part is not in the scene → cad.edit action=\"add_part\""), exact semantics ("pass the position you want, not a delta", "sets an object's absolute position and rotation"), and copy-paste-ready code ("body = Box(40, 30, 12)", "publish(\"body\", body, \"Main body\")", "body_width = param(\"body_width\", 40.0)") covering the common cases.

Workflow Clarity

The Loop section sequences six steps with explicit validation checkpoints ("Inspect the attached preview directly before doing anything else", "if the preview shows anything else, stop and read the scene with cad.inspect") and complete feedback loops for error recovery (previewError handling, stale_build recovery, focused repair). Destructive deletes are also gated: "Deletion commits a normal build and requires a handoff cad.export" with the Undo fallback, so the destructive-operation cap does not apply.

Progressive Disclosure

Sections are well organized (Scene, Placement, Loop, Python Cell Contract, Deleting, Project PCB inputs, Observation Rules, Build Discipline) with one clearly signaled external reference ("Load build123d-core only when specific API syntax or modeling details are needed") and no nested references. Minor gap: longer policy material such as the PCB-comparison checklist is inlined in a ~156-line file where a one-level reference file could carry the detail.

Specificity

The description names a concrete domain ("persistent, visual, short-loop CAD modeling") and enumerates ten specific tools ("cad.open, cad.add_part, cad.edit_part, cad.place, cad.import, cad.delete, cad.look, cad.inspect, ... cad.export"), giving several specific actions with minor gaps in plain-language capability verbs like "export STEP files" or "place components".

Completeness

Both parts are present: "Use for ... CAD modeling" is an explicit when-clause and the tool enumeration states the what. However, the when lacks concrete user-trigger phrases (e.g., "when the user asks to model a part or design an enclosure") and the what lists tools rather than outcomes, so it falls short of the anchor-5 example.

Trigger Term Quality

"CAD modeling" is the natural core trigger a user would say, but common variations and synonyms are missing ("3D model", "part design", "assembly", "enclosure", "STEP"), and the rest of the description is tool-name jargon ("cad.open", "Host-owned CAD Review") users would not naturally say.

Distinctiveness Conflict Risk

The description occupies a clear niche — a host CAD workbench with proprietary cad.* tool names and "Host-owned CAD Review" — so it is clearly distinguishable from generic document, file, or data skills with minimal conflict risk.