---
name: simplecadapi
description: Thin SimpleCAD SDK reference skill focused on the public API surface, core types, and current modeling workflows.
license: AGPL-3.0
compatibility: Documentation/reference bundle for current SimpleCADAPI surfaces.
metadata:
  project: simplecadapi
  version: 2.0.1b1
  package-name: simplecadapi
  package-version: 2.0.1b1
---

# SimpleCAD SDK Skill

## Philosophy
- This is a thin SDK reference skill: docs only.
- SDK source code is not bundled in this skill.

## Working From Repo Root
- Tool calls run from the repo root.
- Use one explicit skill root: `./skills/simplecadapi/` or `./workspace/skills/simplecadapi/`.
- Main doc paths:
  - `<skill_root>/SKILL.md`
  - `<skill_root>/references/docs/api/README.md`
  - `<skill_root>/references/docs/api/<api_name>.md`
  - `<skill_root>/references/docs/stdlib/README.md`
  - `<skill_root>/references/docs/stdlib/<stdlib_api_name>.md`
  - `<skill_root>/references/docs/core/<type_name>.md`
  - `<skill_root>/references/SDK_OVERVIEW.md`
  - `<skill_root>/references/SDK_SURFACES.md`
  - `<skill_root>/references/MODELING_WORKFLOWS.md`

## MUST Requirements
1. Read `SKILL.md`, `references/docs/api/README.md`, and `references/docs/stdlib/README.md` before choosing APIs.
2. Read the exact API Markdown page for every API you use.
3. Read the needed `core/` or exact `api/` docs when an API needs `Edge`, `Face`, `Wire`, `Solid`, `GraphSession`, `Sketch`, or expression types.
4. Prefer the standard parts library for standard parts before hand-modeling with core geometry APIs.
5. Follow the documented API signatures exactly.
6. When calling any SimpleCAD public API or standard-library function, use keyword arguments for every documented parameter; do not use positional arguments.
7. Use the graph/model JSON workflow for replayable tasks: `GraphSession`, `export_session_json`, `export_model_json`, `import_model_json`, and `replay_model_json`.
8. Use geometry APIs for integrated parts: profiles, features, booleans, transforms, tagging, QL inspection, serialization, and exports.
9. Use tags consistently through `apply_tag(shape=..., tag=...)` and `list_tags(shape=...)`; do not call shape member tag mutators.
10. Build and validate incrementally. Each step MUST include a small grounding `print`, and grounding MUST use QL where possible.
11. For inspection/debugging, query geometry with QL and print only the queried facts you need; do not print whole solids or full model objects.
12. Boolean operations return a single `Solid`.
13. Use `union_rsolid(...)` for boolean union.
14. For automated example/test harnesses, prefer the repo-local examples in `examples/` and avoid scratch scripts in `sandbox/`.
15. If union cannot produce exactly one merged solid, it fails explicitly; do not silently pick one piece.
16. If a single merged solid is required and union fails, slightly adjust part placement so intended bodies overlap/embed, then recompute.
17. If a task depends on model replay or interchange, prefer `export_model_json()` output over hand-written payloads.

## Standard Parts Library
- SimpleCAD includes a standard library for parameterized mechanical parts.
- When the user needs a standard part and does not require complex custom geometry changes, use a standard-library function first.
- Current package-level standard-library surfaces include `scad.std.gear` for involute gears, internal ring gears, racks, and cycloidal discs, plus `scad.std.bearing` for ball bearing assemblies.
- Read `references/docs/stdlib/README.md` to discover standard-library functions.
- Read `references/docs/stdlib/<function_name>.md` before calling a standard-library function.
- Standard-library functions return normal SimpleCAD shapes or product assemblies that can be transformed, tagged, assembled, exported, and used with graph/model JSON workflows.

## Boolean result discipline
- `union_rsolid(...)`, `cut_rsolid(...)`, and `intersect_rsolid(...)` accept mixed inputs: standalone `Solid`, lists of `Solid`, and nested sequences.
- They return a single `Solid`.
- `union_rsolid(...)` already applies the package's default glue mode and a conservative internal tolerance.
- If a union cannot produce exactly one merged solid, it fails explicitly instead of returning multiple pieces.
- If a single merged solid is required but union fails, slightly move the parts so they overlap instead of merely touching, then recompute the union.

## Modeling Mental Model
- Start with intent: identify the part, its reference axes, critical profiles, and the features that produce the final solid.
- Build from lower-dimensional geometry to higher-dimensional geometry: `Vertex` / `Edge` / `Wire` / `Face` profiles first, then `Solid` features such as extrude, revolve, loft, and sweep.
- Keep modeling operations functional. Create new values from public functions such as `make_circle_rface(...)`, `extrude_rsolid(...)`, `cut_rsolid(...)`, and `fillet_rsolid(...)`.
- Use keyword arguments for all SimpleCAD function calls, for example `make_box_rsolid(width=10.0, height=20.0, depth=3.0)` instead of positional arguments.
- Use `GraphSession` when the model should be replayable, inspectable, exported as model JSON, or translated to another CAD system.
- Treat model JSON as the interchange boundary. Prefer `export_model_json(session=...)` and `replay_model_json(json_str=...)` over hand-authored operation payloads.
- Use QL for precise grounding. Query faces, edges, centers, normals, areas, lengths, curve types, and tags; print only the facts needed to validate the current step.
- Use `get_edges(index)`, `get_faces(index)`, `get_wires(index)`, or `get_vertices(index)` when an indexed topology pick is intentional; these picks are preserved as geo select nodes in replayable graph workflows.
- Use tags for semantic intent and selection anchors, such as `role.mounting_surface`, `anchor.datum.primary`, `face.top`, or `group.fasteners`.
- Keep numeric and geometric facts in metadata or graph payloads, not in tags.
- When a QL-selected face or edge is used by a later feature, expect the graph/model workflow to preserve that selection as a stable geo select node.
- For FreeCAD translation, prefer canonical model JSON generated from a `GraphSession`; selected profiles and detail-feature selections should come from the graph rather than ad hoc object lookup.

## Tagging Mental Model
- Public tag attachment is `apply_tag(shape=..., tag=...)`.
- Public tag inspection is `list_tags(shape=...)`, which returns a stable sorted list.
- Tags are normalized lowercase dot-separated semantic tokens, for example `role.mounting_surface`, `anchor.datum.primary`, `group.fasteners`, `face.top`, or `solid.boolean.cut`.
- Do not encode numeric dimensions or descriptive geometry payloads in tags; store them in metadata such as `shape.get_metadata("geo")` or `shape.set_metadata(...)`.
- `apply_tag(...)` does not expose propagation controls. The SDK propagates role/anchor/group-style semantic tags downward and keeps topology-specific tags such as `face.*`, `edge.*`, `wire.*`, `vertex.*`, and `solid.*` local.
- Primitives, face auto-tagging, features, booleans, transforms, and tracking may add normalized topology/operation tags automatically.
- Prefer QL tag predicates (`ql.tag("role.*")`, `ql.select(...).where(...)`) for inspection and grounding.

## SDK Focus
- This skill is intended to describe the public CAD Python SDK surface.
- Prefer the generated API, stdlib, and core docs over environment/bootstrap instructions.
- API docs include an `Import Surface` section that distinguishes top-level exports, submodule APIs, and translator backend APIs under `simplecadapi.translator.<backend>`.
- Stdlib docs include an `Import Surface` section that identifies the package-level `simplecadapi.std.gear` module export.
- Use `references/SDK_OVERVIEW.md` for the package-level map.
- Use `references/SDK_SURFACES.md` for the main public surfaces.
- Use `references/MODELING_WORKFLOWS.md` for graph/model-oriented patterns.

## Example SDK usage

```python
import simplecadapi as scad
from simplecadapi import GraphSession, export_model_json, make_box_rsolid
```

Typical replayable usage in a Python script:

```python
import simplecadapi as scad
from simplecadapi import GraphSession, export_model_json, replay_model_json

with GraphSession() as session:
    shape = scad.make_box_rsolid(width=10.0, height=20.0, depth=30.0)

model_json = export_model_json(session=session)
rebuilt = replay_model_json(json_str=model_json)
print(len(rebuilt))
```

Use the graph/model JSON workflow when the task needs reproducibility, interchange, or replayable outputs.

## References
- `references/SDK_OVERVIEW.md`
- `references/SDK_SURFACES.md`
- `references/MODELING_WORKFLOWS.md`
- `references/SDK_PACKAGE_SUMMARY.md`
- `references/docs/api/`
- `references/docs/stdlib/`
- `references/docs/core/`