AEE MCP Server

Accessibility Evidence Engine (AEE)


AI-first accessibility testing that augments your existing Playwright tests.

axe tells you the alt attribute exists. AEE tells you whether the alt text is _right_ — and writes you a better one.

Static scanners (axe-core) answer "is the attribute present?" and top out around 30–50% of real issues, because the defects that matter — a meaningless alt, an icon button named "button", a heading that doesn't describe its section, meaning carried by color alone — are not statically detectable. AEE puts an AI judgment layer on top of that deterministic floor and asks "is it correct in this context?", returning a verdict, a grounded reason, a suggested fix, and a reliability tier.

AEE is agent-native: you operate it by chat through an MCP server (run investigations, query the evidence, apply fixes), declare a page's intent in plain language to sharpen judgments, chat with the report locally, and let it open remediation PRs.

Status: implemented end to end and verified on a local model — no API key. Coverage spans Tier 1 (naming), Tier 2 vision (color-alone, focus-visible, text-in-images), Tier 3 dynamic (focus, live regions, keyboard), the Tier 4 axe-core floor, and Tier 5 advisory (never a certified PASS). The agent surfaces (MCP, triage) and remediation (fix) are real. See docs/ROADMAP.md for current state and docs/PLAN.md for the architecture.

How it works

Playwright test → observers capture EVIDENCE → AI judges quality (evidence only) → REPORT + fixes
                                                         ↑
                              AI-first surfaces: MCP server · triage UI · auto-fix/PR

The core invariant: AI sees captured evidence only, never the live page — so judgments are grounded and reproducible, and the rule UNKNOWN never becomes PASS holds.

Packages

| Package | Role | | --- | --- | | @aee/core | Contracts, zod schemas, evidence/judge/report types (depends on zod only) | | @aee/observers | Evidence grounding: DOM, a11y tree, screenshots, images, styles, network, SR | | @aee/ai | AI judgment + conversational explain() + fix drafting (evidence only) | | @aee/judges | Per-concern judges = axe-core floor + AI judgment | | @aee/playwright | Driver + test fixture + checkpoint() | | @aee/reporter | JSON report + terminal summary | | @aee/mcp | MCP server — the agent-native surface | | @aee/triage | Local "chat with your report" UI | | @aee/fix | Apply suggested fixes and open PRs |

Quickstart — drop-in Playwright fixture

import { test, expect } from '@aee/playwright'; // drop-in for '@playwright/test'

test('checkout flow', async ({ page, aee }) => {
  await page.goto('/checkout');
  await aee.checkpoint('checkout-loaded', {
    intent: { purpose: 'Checkout', primaryAction: 'Pay', notes: 'cart icon opens the cart drawer' },
  });
  // ...your existing test, unchanged...
});

Talk to it — the MCP server

AEE is agent-native: a coding agent (Claude Code, Cursor, …) connects to the MCP server and investigates pages by chat. Build, then run it over stdio:

pnpm build
node packages/mcp/dist/bin.js      # or `aee-mcp` once the package is linked

Register it like any stdio MCP server — local model, no API key:

{ "mcpServers": { "aee": {
  "command": "node",
  "args": ["/abs/path/accessibility-engine/packages/mcp/dist/bin.js"],
  "env": { "AEE_LLM_PROVIDER": "local" }
} } }

Then investigate a page (→ a graded report with fixes), explain a finding from evidence, suggest_fix (→ targeted FixPlans), and apply_fix (→ patches the fixes into source). Full reference: docs/mcp-tools.md.

Development

pnpm install
pnpm build       # tsc -b across all packages
pnpm typecheck
pnpm test        # node --test over built dist/
pnpm gen:schemas # regenerate JSON Schema in /schemas from the zod source
pnpm demo        # investigate a sample page and print the graded report

Requires Node ≥ 22 and pnpm. pnpm demo needs Chromium (pnpm exec playwright install chromium); set AEE_LLM_PROVIDER=local (with a local server running) to judge for real — otherwise AI verdicts are UNKNOWN and the axe floor still reports.

Model backends (no API key required)

The AI layer is provider-agnostic: it depends on a one-method JudgmentModel seam, not on any SDK. Pick a backend with createAIClient({ provider }) or the AEE_LLM_PROVIDER env var.

| Provider | Backend | Needs | | --- | --- | --- | | local | A local model over the OpenAI-compatible API (Ollama, LM Studio, llama.cpp, vLLM, …) | a running local server — no key | | claude | Anthropic Claude (claude-opus-4-8 by default) | ANTHROPIC_API_KEY | | stub | Always-UNKNOWN (the default when no key is set) | nothing |

Run the engine against a local model — no key, no cloud:

# Ollama (default base URL http://localhost:11434/v1)
export AEE_LLM_PROVIDER=local
export AEE_LLM_MODEL=gemma4:e4b      # any chat model you have pulled
pnpm test                            # the local live tests now exercise real judging

Point AEE_LLM_BASE_URL at LM Studio (http://localhost:1234/v1), llama.cpp, vLLM, or any OpenAI-compatible endpoint. A local judgment that can't be reached or parsed degrades to UNKNOWN — never a guessed PASS.

License

MIT