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.

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

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

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:

Runs ${CLAUDE_SKILL_DIR}/../_shared/scripts/cdp-bridge.js tree (full fiber tree output)
Extracts a11y props from each component: accessible, accessibilityLabel, accessibilityRole, accessibilityHint, accessibilityState, accessibilityValue, importantForAccessibility, role, aria-label, aria-hidden
Compares React-declared a11y props against the native accessibility tree report from Step 1 (passed to subagent as context)
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

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

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).