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shell_part

Hollow out a solid body to a specified wall thickness, leaving selected faces open for openings. Ideal for creating cast housings or plastic enclosures.

Instructions

Vaciado de pared (shell) — hollow out the body, optionally removing the listed faces to leave openings.

selector (recommended) — pick the open face(s) by INTENT, e.g. leave the top face open: selector={"filter": {"geom": "planar", "normal_axis": "+z"}}. Same face-selector schema as create_sketch_on_face (filter geom/body/normal_axis/axis/area, sort, pick). May match several faces (each becomes an opening). Mutually exclusive with face_centroids_mm.

Junior workflow: "haz un vaciado de 2mm dejando la cara superior abierta" — common for cast housings (carcasas), plastic enclosures (gabinetes), and any hollow case with an opening. SolidWorks shells the entire body to the given wall thickness; faces listed in face_centroids_mm become open holes.

Args: thickness_mm: Espesor de pared (wall thickness) in mm. Must be positive and less than half the smallest body dimension — SW silently rejects thicknesses too large to fit. face_centroids_mm: Faces to leave open. Pass a list of [x, y, z] centroids from list_faces(). None or [] = closed shell (the whole body hollowed, no openings). Each centroid must match a real face within 0.01 mm. outward: False (default) puts the shell wall INSIDE the original surface — the standard "hollow housing" intent. True keeps the shell outside (offset surface outward) — rare; only for special cases.

Returns the new Vaciado feature (type=shell, D1=thickness_mm).

Caveat: shell is destructive of subsequent face-anchored sketches — faces shift to the new offset surfaces. Run shell_part LATE in the feature tree, after all face-anchored boses/cuts are placed.

Example — 2mm-walled cup, 50×50×40 mm with the top open: create_sketch("front") create_rectangle(0, 0, 50, 50) extrude_sketch(40) faces = list_faces() top = max( (f for f in faces if f["normal"][2] > 0.9), key=lambda f: f["centroid_mm"][2], ) shell_part(2.0, face_centroids_mm=[top["centroid_mm"]])

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
outwardNo
selectorNo
thickness_mmYes
face_centroids_mmNo
Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description fully discloses behavior: destructive of face-anchored sketches, thickness constraints, centroid matching tolerance, and outward parameter effect. This is comprehensive.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is lengthy but well-structured with overview, details, caveats, and example. Every sentence adds value, though slightly verbose; still appropriate for the tool's complexity.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Despite no output schema or annotations, the description covers all necessary aspects: purpose, parameters, constraints, behavior, caveats, and a concrete example. It is fully sufficient for correct usage.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

All four parameters are explained in detail: thickness constraint, face_centroids source from list_faces, outward meaning, and selector vs face_centroids mutual exclusivity. The description adds significant value beyond the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool hollows out a body (shell) with optional openings. It uses specific verbs and resources, and distinguishes from sibling operations like extrude or revolve.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides context on when to use shell (common for cast housings, plastic enclosures) and warns to run late in feature tree. It could explicitly name alternatives but gives sufficient guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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