SCAD Library Policy Skill

Use this skill when deciding whether generated OpenSCAD may include external libraries.

Purpose

AgentSCAD should use reusable CAD libraries as infrastructure, not hardcode product-family geometry in TypeScript.

Approved Behavior

• Prefer approved OpenSCAD libraries when the runtime prompt says they are available.
• Use libraries to improve general CAD quality: rounded boxes, fillets, chamfers, anchors, transforms, arrays, threads, gears, fasteners, text, and mechanical primitives.
• Keep all user-editable dimensions as top-level numeric OpenSCAD assignments.
• Keep output exportable by the configured OpenSCAD renderer.
• Use portable built-in OpenSCAD primitives when no library is available.

Runtime Contract

• The harness reports available libraries before generation.
• The model must not invent include paths.
• The renderer controls the library search path with OPENSCADPATH.
• The repository must not copy third-party library source code unless a human explicitly reviews licensing and approves vendoring.

Preferred Libraries

• BOSL2 for modern rounded solids, transforms, attachments, anchors, arrays, and mechanical utilities.
• NopSCADlib for electronics enclosures, real-world vitamins, assemblies, boards, fans, fasteners, and printer/electronics hardware.
• Round-Anything for rounded sketch profiles, controlled fillets, rounded plates, brackets, tabs, and consumer-product-style softened extrusions.
• MCAD for established OpenSCAD mechanical primitives, especially involute gears.
• threads.scad or threadlib for printable threaded connectors, taps, bolts, nuts, and threaded holes.

Library Skill Prompting

• Load the matching detailed library skill only when the runtime resolver confirms the library is available.
• Include the exact include or use statement discovered by the runtime resolver; do not substitute a guessed path.
• Prefer the narrowest library import needed for the job. For example, prefer use <MCAD/involute_gears.scad> over broad MCAD includes when generating a gear.
• Use one thread library per artifact. Do not mix threads.scad and threadlib in the same generated model.

Hard Rules

• Do not copy BOSL, BOSL2, MCAD, CADAM, or any third-party source code into generated SCAD or the repository.
• Do not encode product-family geometry in TypeScript to fake quality.
• Do not move deterministic validation, rendering, file IO, or database writes into prompts.
• Do not use unavailable libraries.

Output Guidance

When libraries are available, generated SCAD may start with lines like:

include <BOSL2/std.scad>

Only use include statements listed by the runtime prompt.

Scripts

Use deterministic scripts when checking a workstation or generated artifact:

• scripts/check_scad_libraries.py: inspect OpenSCAD library search paths and report which approved libraries are installed.
• scripts/install_scad_libraries.py: install approved app-managed OpenSCAD libraries into ~/.agentscad/openscad-libraries; defaults exclude GPL libraries.
• scripts/validate_scad_includes.py <file.scad>: fail if a generated SCAD file uses unavailable or unapproved library include/use statements.

License Gate

• Install permissive or weak-copyleft libraries by default only when the manifest marks default_install: true.
• Require explicit --include-gpl for GPL libraries such as NopSCADlib.
• Preserve each upstream repository's license files in the managed library directory.
• Keep GPL libraries out of default app bundles unless a human explicitly approves the distribution model.