/extract-structure

name: extract-structure
description: Interpret a component's structure spec (variant axes, dimensions, sub-components, slot contents, cross-variant diffs) from the `_base.json` produced by the uSpec Extract Figma plugin, and write the normalized JSON to disk. Read-only interpretation — no Figma calls except an optional tiny delta script. Use as a sub-skill of create-component-md.

Extract Structure Data

Interpretation-only companion to `create-structure`. This skill **does not extract data from Figma**. It reads `{cachePath}/{componentSlug}-_base.json` (produced by the uSpec Extract Figma plugin), applies the same reasoning layer as `create-structure`, and writes the normalized `StructureSpecData` JSON to disk for the `create-component-md` orchestrator to consume.

**Quality contract:** every reasoning step (section planning, ownership resolution, override promotion, design-intent notes, anomaly detection) mirrors `create-structure/SKILL.md`. Any improvement to structure-extraction quality must be made in both places.

**Batch-mode contract.** This skill MUST NOT call `AskQuestion`, prompt for confirmation, or pause for user input. When a value cannot be resolved from `_base.json` (and a Step 3-delta doesn't recover it), emit a row with `provenance: "not-measured"` and `values: ["—", …]` instead of asking. No mid-interpretation clarifications.

Invocation Contract

The orchestrator calls this skill with these inputs (already resolved — do NOT re-parse URLs or re-read `uspecs.config.json`):

• `componentSlug` — filename-safe slug
• `cachePath` — cache directory, typically `.uspec-cache/{componentSlug}/`
• `optionalContext` — free-form string from the user (may be `"none"`)
• `mcpProvider` — `figma-console` or `figma-mcp` (only used if a Step 3-delta escape hatch fires)
• `deltaAvailable` — boolean derived from `_base.json._meta.fileKey` + `nodeId`. Plugin exports normally make this `true`; a separately-passed `figmaLink` is not required.
• `apiDictionaryPath` — absolute or workspace-relative path to `{cachePath}/{componentSlug}-api-dictionary.json`. Optional. When present, this file is the canonical vocabulary for axis/value/sub-component/state naming (see Step 2.5). When absent, the skill continues with `_dictionaryUnavailable: true` in its output envelope and the renderer treats the produced cache as lower-confidence.
• `evidencePath` — optional. Path to `{cachePath}/{componentSlug}-evidence-structure.json` from CLI prepare. When present and hash-valid, use `data` as the Step 3 working evidence set.

`fileKey` and `nodeId` are **not** pass-through parameters anymore. Read them from `{cachePath}/{componentSlug}-_base.json._meta.fileKey` and `_meta.nodeId` at the start of Step 1.

**Output:**

• Writes `{cachePath}/{componentSlug}-structure.json` containing the full `StructureSpecData` object.
• Returns a single-line summary to the orchestrator: `"Structure extracted: N sections, M sub-components, K slot contents → {path}"`.
• Never creates or mutates Figma nodes.

MCP Adapter

This skill typically makes **zero** MCP calls — it reads `_base.json` from disk. The adapter applies only to the optional Step 3-delta escape hatch.

| Operation | `figma-console` | `figma-mcp` | |-----------|-----------------|-------------| | Execute Plugin JS (delta only) | `figma_execute` with `code` | `use_figma` with `fileKey`, `code`, `description` |

For `figma-mcp` delta scripts, include the page-focus preamble after `getNodeByIdAsync`:

let _p = node; while (_p.parent && _p.parent.type !== 'DOCUMENT') _p = _p.parent;
if (_p.type === 'PAGE') await figma.setCurrentPageAsync(_p);

Workflow

Task Progress:
- [ ] Step 1: Read instruction file
- [ ] Step 2: Load _base.json and optionalContext
- [ ] Step 2.5: Load API dictionary (canonical vocabulary) — optional
- [ ] Step 3: Build working evidence set (from _base.json fields only)
- [ ] Step 3-delta: OPTIONAL — read-only Figma call if a fact is genuinely missing
- [ ] Step 4: AI interpretation layer — section plan, ownership, design-intent notes, anomalies
- [ ] Step 5: Generate StructureSpecData object
- [ ] Step 6: Audit (re-read instruction file)
- [ ] Step 7: Write JSON to cache and return one-line summary

Step 1: Read Instructions

Read [agent-structure-instruction.md]({{ref:structure/agent-structure-instruction.md}}). This is the **same** instruction file used by `create-structure`. Treat it as the single source of truth for the `StructureSpecData` schema, row emission rules, and audit checklists.

Rendering-only sections to skip

The shared instruction file describes both extraction and Figma rendering. This skill only performs interpretation — ignore guidance in the sections below. The data schema and audit checklists still apply.

• **§Role — "render structure documentation directly into Figma"** — framing only; this skill writes JSON to disk instead.
• **§Inputs — the `figma_execute` row's "render sections" phrasing** — this skill does not render.
• **§Data Structure Reference — "The data is passed directly into Figma template placeholders — no JSON output is needed"** — inverted: we **do** output JSON. Keep the schema; discard the "no JSON" framing.
• **§Field Rules — "Render order: first column → values[0..n] → Notes", "Renders between Spec and Notes columns", "Always renders in the final Notes column"** — rendering-order prose. The `spec` / `values[]` / `notes` shape is still the authoritative schema.
• **§Common Mistakes — "Overriding preview frame layout" and any bullet about `#Preview` frame behavior** — rendering concerns. Data-level mistakes (missing sub-component sections, wrong axis grouping, bad display strings) still apply.
• **§Pre-Render Validation Checklist — "Sub-component preview sourcing" and "Preview frame untouched" rows** — do not apply. All other checks (shape of `sections`, correctness of `rows`, column counts, measurement labels) DO still apply.
• **§Inputs → "Authoritative