aieng-cad-authoring

aieng-cad-authoring

MCP-first CAD authoring discipline for agents driving the active AIENG Workbench. The recommended path is the live MCP toolchain and build123d runtime, not the older schema-plan CLI flow.

Purpose

• Create or extend real CAD geometry through cad.execute_build123d.
• Keep generated geometry inspectable with named parts, colors, and editable constants.
• Use the UI as the live 3D viewer and spatial pointer surface.
• Preserve evidence honesty: CAD output is geometry evidence, not engineering validation.

When to use

Use when the user asks to create, build, design, model, add, or substantially modify CAD geometry. For pure dimensional tweaks on an existing editable model, prefer cad.edit_parameter. For engineering audit only, use cad.critique without mutating geometry. For solver workflows, use aieng-cad-cae-copilot.

Required workflow

1. Call aieng.agent_readme, aieng.list_projects, and aieng.agent_context { project_id } when project state is not already known.
2. Call cad.get_source { project_id } before incremental edits; use mode="append" only when has_base=true.
3. For new/additive geometry, call cad.execute_build123d with build123d Python that:
   • binds the final model to result,
   • omits export calls,
   • sets .label on every meaningful part,
   • sets .color = Color(r,g,b) for readability,
   • declares editable dimensions as UPPER_SNAKE_CASE constants,
   • asserts design intent with require(condition, "message") — e.g. require(WALL_THICKNESS >= 3, "wall below 3mm CNC minimum"). A failed require() (or a bare assert) fails the build deterministically and is returned as a structured code: design_rule_violation, so constraints are verified by construction instead of hoped for; a passing one is a no-op.
4. Inspect the returned thumbnail, named_parts, parts_added, geometry_report_summary, symmetry, and gaps before continuing.
5. For pure dimensional changes, use cad.edit_parameter and read both regression_diff (topology drift) and critique_diff (manufacturability) before trusting the result.
6. For mechanical parts, call cad.critique after creation and fix blocking manufacturability findings.