a11y-toolkit

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a11y-toolkit: Express WCAG audit

a11y_audit_url

Read-onlyIdempotent

Audit a URL or raw HTML for WCAG 2.2 accessibility issues and get a weighted 0–100 score, findings, and remediation steps.

Instructions

Express WCAG 2.2 audit of a URL or an HTML string: 20+ automated signals with a weighted 0-100 score — images without alt (1.1.1), low-quality alt text (filenames, generics, placeholders; also 1.1.1), controls without accessible names (4.1.2), form fields without labels (3.3.2), missing autocomplete on user-data fields (1.3.5), click handlers on non-interactive elements (2.1.1), unknown ARIA roles and broken aria-labelledby (4.1.2), duplicated unnamed landmarks, timed meta refresh (2.2.1), missing skip mechanism (2.4.1), lang/title (3.1.1, 2.4.2), heading structure (1.3.1), blocked zoom (1.4.4), captions (1.2.2), autoplay audio (1.4.2), generic/duplicated link text (2.4.4), target=_blank without warning (3.2.5), positive tabindex (2.4.3), aria-hidden on focusable elements, tables without th, duplicate ids, duplicate accesskeys. Each finding includes concrete remediation. Filter, not verdict: automation covers ~1/3 of WCAG; query a11y_criterion for what a criterion means. — Prefer a11y_audit_dom when JS renders the content or contrast/2.5.8/focus matter; use pages for light multi-page sampling. Static CANNOT measure class/var() CSS contrast (1.4.3): the report's not_measured says so — a 100 is never 'contrast is fine'. Returns JSON: {mode, url|file, score 0-100, findings [{criterion, severity, signal, issue, remediation}], summary {high, medium, low}, limits, score_note, overlay_widgets? (detected third-party overlay scripts — data, not a WCAG finding)}.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "a11y_audit_url"
  }
}

Input Schema

Name	Required	Description
`url`	No	URL to fetch and audit
`html`	No	raw HTML to audit directly (overrides url)
`lang`	No	output language (en default)
`pages`	No	light same-domain crawl: audit up to N pages, aggregated by score and recurring signals (default 1, max 20)
`target`	No	EN 301 549 target: web=9.x clauses (default), documents=10.x, software=11.x
`timeout`	No	fetch timeout seconds (30 default)
`standard`	No	en301549: EN clause per finding (EAA procurement, Canada ICT) · rgaa: French RGAA criterion per finding

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv5.27.0Nov 10, 2026

addedInput schema / properties / standard

Added value: +{
+  "description": "en301549: EN clause per finding (EAA procurement, Canada ICT) · rgaa: French RGAA criterion per finding",
+  "enum": [
+    "en301549",
+    "rgaa"
+  ],
+  "type": "string"
+}

addedInput schema / properties / target

Added value: +{
+  "description": "EN 301 549 target: web=9.x clauses (default), documents=10.x, software=11.x",
+  "enum": [
+    "web",
+    "documents",
+    "software"
+  ],
+  "type": "string"
+}

Changed2 schema fields changedv5.5.0Oct 14, 2026
- addedInput schema / properties / pages / maximum
```
Added value: +20
```
- addedInput schema / properties / pages / minimum
```
Added value: +1
```
Changed1 schema field changedv3.12.0Sep 15, 2026
- changedInput schema / properties / lang / description
```
Previous value: -"output language (es default)"New value: +"output language (en default)"
```

Changed6 schema fields changedv3.3.0Sep 13, 2026

addedInput schema / properties / html

Added value: +{
+  "description": "raw HTML to audit directly (overrides url)",
+  "type": "string"
+}

addedInput schema / properties / lang / description
```
Added value: +"output language (es default)"
```

addedInput schema / properties / pages

Added value: +{
+  "description": "light same-domain crawl: audit up to N pages, aggregated by score and recurring signals (default 1, max 20)",
+  "type": "integer"
+}

addedInput schema / properties / timeout

Added value: +{
+  "description": "fetch timeout seconds (30 default)",
+  "type": "number"
+}

addedInput schema / properties / url / description
```
Added value: +"URL to fetch and audit"
```
removedInput schema / required
```
Removed value: -[
-  "url"
-]
```

First observedv2.3.0Aug 23, 2026

TDQS

A4.6/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare read-only, open-world, idempotent, and non-destructive behavior, but the description adds substantial context: automation covers roughly one third of WCAG, a score of 100 does not mean contrast is fine because static analysis cannot measure class/var() contrast, and the report includes not_measured and limits. It also explains that findings include remediation and that overlay_widgets are data rather than WCAG findings.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The purpose and main limitations are front-loaded, and most of the length is substantive: enumerated audit signals, sibling-tool routing, and the return shape. The prose is dense and could be more scannable if the long signal list were structured, but there is little redundant filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

There is no output schema, but the description provides a detailed return shape including score, findings, summary counts, limits, score_note, and overlay_widgets. Combined with the explicit scope, limitations, and sibling guidance, it is complete enough for an agent to invoke this complex open-world audit tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the input schema already documents url, html override behavior, pages crawl semantics, lang, target, timeout, and standard. The description lightly reinforces URL/HTML input and the pages use case, but adds little parameter meaning beyond the schema, making the baseline 3 appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: an express WCAG 2.2 audit of a URL or HTML string, scoped to 20+ automated signals with a weighted 0-100 score. It also explicitly distinguishes itself from a11y_audit_dom by noting JS-rendered content and contrast/focus scenarios.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly says to prefer a11y_audit_dom when JS renders the content or contrast/2.5.8/focus matter, use pages for light multi-page sampling, and query a11y_criterion for criterion meanings. It also frames the tool as a filter rather than a verdict, giving clear when-to-use and when-not-to-use guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.