Skill: a11y-audit

On load: Read ../../.claude-plugin/plugin.json from this skill's base directory. Display a11y-audit v{version} before proceeding.

Audit the accessibility tree of a running React Native app in the iOS Simulator against official React Native accessibility documentation.

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Dependencies

Skill / Resource	Why
ios-sim	ui.sh describe-all captures the accessibility tree; capture.sh view used for optional screenshot context
_shared (metro.sh, cdp-bridge.js)	Optional Step 1.5 — extracts React-declared a11y props via CDP when Metro is running

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Severity Levels

Level	Meaning	Examples
Critical	Blocks screen reader users	Interactive element without accessibilityLabel; image without label
Warning	Degrades experience	Touch target < 44x44pt; missing accessibilityRole on button
Info	Improvement opportunity	Missing accessibilityHint; elements that could be grouped

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Workflow

Pre-check

Before dispatching the subagent, verify AXe is installed:

Run: command -v "${IOS_SIMULATOR_MCP_AXE_PATH:-axe}" >/dev/null 2>&1

If this fails, stop and tell the user: "a11y-audit requires AXe to read the accessibility tree. Install with: brew install cameroncooke/axe/axe Then re-run this skill."

Do not dispatch the subagent if AXe is missing — it will fail immediately.

Step 1 — Capture and audit the accessibility tree (subagent)

Never load the accessibility tree in main context. Dispatch a subagent.

Dispatch Agent:
  subagent_type: general-purpose
  model: haiku
  description: "a11y-audit: capture and analyze accessibility tree"
  prompt: |
    You are auditing the accessibility of a React Native app running in the iOS Simulator.

    1. Run: ${CLAUDE_SKILL_DIR}/../ios-sim/scripts/ui.sh describe-all
       This outputs the full accessibility tree as JSON.

    2. Read the checklist: ${CLAUDE_SKILL_DIR}/references/a11y-checklist.md

    3. Walk every element in the tree. Check for these issues:

       CRITICAL:
       - Interactive elements (buttons, links, switches, text fields) without accessibilityLabel
       - Images without an accessibility label
       - Elements with an accessibilityLabel that is just a filename or empty string

       WARNING:
       - Interactive elements without accessibilityRole or role
       - Touch targets smaller than 44x44 points (check frame width/height)
       - Nested accessible elements (accessible parent containing accessible children)
       - Toggle/checkbox elements missing accessibilityState

       INFO:
       - Interactive elements missing accessibilityHint
       - Potential grouping opportunities (adjacent related elements)
       - Static text elements that could use a header role

    4. Return a structured text report in this exact format:

       ACCESSIBILITY AUDIT REPORT
       ==========================
       Total elements scanned: <N>
       Issues found: <N> critical, <N> warning, <N> info

       CRITICAL ISSUES
       ---------------
       1. [element description] at (x, y) — Missing accessibilityLabel
          Fix: Add accessibilityLabel="<suggested label>"
       ...

       WARNINGS
       --------
       1. [element description] at (x, y) — Touch target too small (WxH)
          Fix: Add hitSlop or increase padding to at least 44x44pt
       ...

       INFO
       ----
       1. [element description] — Missing accessibilityHint
          Suggestion: Add accessibilityHint="<suggested hint>"
       ...

       If no issues in a category, write "None found."
    Return text only. Be thorough but concise.

Step 1.5 — React A11y Props (optional)

If Metro/Hermes debugger is available, extract React-declared accessibility props from the fiber tree and compare against the native accessibility tree from Step 1.

Guard: Run ${CLAUDE_SKILL_DIR}/../_shared/scripts/metro.sh status. If exit code is 1 (Metro not running), skip silently to Step 2.

If Metro is running:

Dispatch a subagent that:

1. Runs ${CLAUDE_SKILL_DIR}/../_shared/scripts/cdp-bridge.js tree (full fiber tree output)
2. Extracts a11y props from each component: accessible, accessibilityLabel, accessibilityRole, accessibilityHint, accessibilityState, accessibilityValue, importantForAccessibility, role, aria-label, aria-hidden
3. Compares React-declared a11y props against the native accessibility tree report from Step 1 (passed to subagent as context)
4. Returns a DISCREPANCIES report listing:
   • Components with React a11y props that don't appear in native tree
   • Components in native tree missing expected React a11y props
   • Mismatches between declared labels/roles and native values

Why subagent: Full fiber tree is 10-100 KB, too large for main context. The subagent processes it and returns only the discrepancy report (~1-3 KB).

Step 2 — Enrich with documentation references

After the subagent returns its report, grep the React Native docs for relevant best practices. If CDP data is available from Step 1.5, add a DISCREPANCIES section comparing React-declared props against native a11y tree values.

Grep "${CLAUDE_SKILL_DIR}/../../refs/react-native-docs/accessibility.md" for key terms
from the audit (e.g., accessibilityLabel, accessibilityRole, accessibilityHint).

Read specific sections only if needed to provide accurate fix guidance.

Step 3 — Present final report

Combine the subagent audit report with doc references:

• Show the full issue list with counts by severity
• For each critical issue, include the fix with a citation to accessibility.md
• Summarize top 3 actions to improve accessibility
• If the app has zero critical issues, congratulate the developer

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Context Efficiency

Item	Size	In Main Context?
Accessibility tree JSON	~10-100 KB	NEVER — subagent only
Audit checklist	~4 KB	Subagent only
Subagent text report	~1-3 KB	YES
CDP a11y discrepancy report	~1-3 KB	YES (from subagent)
Doc grep results	~200-500 chars	YES

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Tips

• The iOS Simulator must be booted with an app running. Use ios-sim skill to launch if needed.
• Point coordinates from the accessibility tree are in logical points, not pixels.
• Touch target audit uses the element's frame dimensions from the tree.
• For Android-specific audits (48x48dp), a physical device or emulator with adb is needed (not covered by this skill).