freecad-parametric-expert

name	FreeCAD Parametric Expert
description	Multi-agent orchestration skill for producing production-ready parametric CAD models in FreeCAD 1.1 via the Robust MCP bridge. Implements a Sketch Designer → API Agent → Geometry Verifier loop with automatic retry on failure.

FreeCAD 1.1 Parametric Expert — Orchestration Skill

This skill defines a deterministic multi-agent pipeline for generating logically sound, production-ready parametric CAD models through the Robust MCP bridge. It prevents the most common LLM-CAD failure modes: the Topological Naming Problem, non-manifold geometry, zero-volume extrusions, and broken sketch constraints.

Orchestration Loop

When the user requests a parametric part, you must follow one of the orchestration loops below. Do not skip the verification step.

Route A: Native FreeCAD 1.1 Pipeline

Use this route for highly parametric models requiring native spreadsheet control directly in FreeCAD.

[User Input] ──► [Sketch Designer] ──► [FreeCAD API Agent] ──► [Geometry Verifier]

Route B: CadQuery Pipeline (Zero-To-CAD-1m)

Use this route for fast generative builds, leveraging the synthetic patterns proved by the Zero-To-CAD-1m dataset.

[User Input] ──► [CadQuery API Agent] ──► [STEP Export] ──► [FreeCAD Import] ──► [Geometry Verifier]

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Zero-To-CAD-1m Dataset Integration

The workspace includes scripts to pull reference models from the 1-million-part synthetic dataset:

• Run python scripts/download_zero_to_cad.py to cache parquet validation partitions and extract CadQuery templates.
• Use these templates as few-shot context when generating complex mechanical parts via the CadQuery API Agent.

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Key API Changes (FreeCAD 1.1+)

Legacy	FreeCAD 1.1+	Notes
Support	AttachmentSupport	Sketch attachment
DataSupport	DataAttachmentSupport	Data layer
MapMode values	Same	Critical for sketch alignment
Sub-property placement	obj.Placement = App.Placement(...)	Single recompute trigger

Safe Attachment Pattern

sketch.AttachmentSupport = [(body, 'XY_Plane')]
sketch.MapMode = 'FlatFace'
doc.recompute()

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Stability Best Practices

1. Atomic Operations: Never combine Document Creation, Sketching, and Padding in a single execute_python call. Split them to let the bridge breathe between recomputes.
2. Explicit Recompute: Call doc.recompute() after each complete feature. Never recompute inside high-frequency loops.
3. Spreadsheet First: Initialize parameters in a Spreadsheet::Sheet named Params before creating geometry so expressions have valid targets.
4. Queue Flushing: Wait ~2 seconds between calls when the bridge is sluggish to let the GUI thread flush its event queue.

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Optimization Rules

Isolate via Custom Spreadsheets

All parametric adjustments must be made by modifying spreadsheet cell values through MCP, not by rewriting sketch geometry code. The LLM must never edit an existing complex script block — it must only change cell values.

Keep Context Clean

Once a step is verified, clear the generation context. Pass only the resulting Params alias map to the next stage. This prevents token bloat and reduces hallucination risk in later stages.

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Agent Blueprints

Agent	File	Responsibility
Sketch Designer	Agent_SketchDesigner.md	2D geometry, constraints, parametric binding
FreeCAD API Agent	Agent_FreeCAD_API.md	Translates geometric plan into atomic FreeCAD Python
CadQuery API Agent	Agent_CadQuery_API.md	Generates CadQuery scripts, exports STEP, and imports into FreeCAD
Geometry Verifier	Agent_GeometryVerifier.md	Validates shape integrity before finalization

Verification Scripts

Script	File	Purpose
Shape validator	verify_geometry.py	Checks manifold, volume, constraint solver status
Zero-To-CAD downloader	download_zero_to_cad.py	Downloads, extracts, and summarizes Zero-To-CAD dataset samples
Bridge restart	restart_bridge.py	Recovers the MCP bridge without restarting FreeCAD