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Web Accessibility MCP Server

by bilhasry-deriv
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MCP-Server für Web-Zugänglichkeit

Schmiedeabzeichen

Ein MCP-Server (Model Context Protocol), der mithilfe von Axe-Core und Puppeteer Funktionen zur Analyse der Webzugänglichkeit bereitstellt.

Merkmale

  • Analysieren Sie die Webzugänglichkeit beliebiger URLs mit axe-core

  • Simulieren Sie Farbenblindheit (Protanopie, Deuteranopie, Tritanopie) mithilfe von Farbmatrizen

  • Detaillierte Berichterstattung über Barrierefreiheitsverletzungen

  • Unterstützung für benutzerdefinierte Benutzeragenten und Selektoren

  • Debug-Protokollierung zur Fehlerbehebung

  • Umfassende Barrierefreiheitsprüfungen basierend auf den WCAG-Richtlinien

Related MCP server: Cursor A11y MCP

Voraussetzungen

  • Node.js (v14 oder höher)

  • npm

Installation

Installation über Smithery

So installieren Sie den Web Accessibility MCP Server für Claude Desktop automatisch über Smithery :

npx -y @smithery/cli install @bilhasry-deriv/mcp-web-a11y --client claude

Manuelle Installation

  1. Klonen Sie das Repository:

git clone [repository-url]
cd mcp-web-a11y

  1. Installieren Sie Abhängigkeiten:

npm install

  1. Erstellen Sie den Server:

npm run build

Konfiguration

Fügen Sie den Server zu Ihrer MCP-Einstellungsdatei hinzu (normalerweise unter ~/Library/Application Support/Code/User/globalStorage/saoudrizwan.claude-dev/settings/cline_mcp_settings.json ):

{
  "mcpServers": {
    "web-a11y": {
      "command": "node",
      "args": ["/path/to/mcp-web-a11y/build/index.js"],
      "disabled": false,
      "autoApprove": [],
      "env": {
        "MCP_OUTPUT_DIR": "/path/to/output/directory"
      }
    }
  }
}

Umgebungsvariablen

  • MCP_OUTPUT_DIR : Verzeichnis, in dem Screenshot-Ausgaben gespeichert werden

    • Erforderlich für das Tool simulate_colorblind

    • Wenn nicht angegeben, wird standardmäßig „./output“ relativ zum aktuellen Arbeitsverzeichnis verwendet.

    • Muss ein absoluter Pfad sein, wenn in den MCP-Einstellungen konfiguriert

Verwendung

Der Server bietet zwei Tools: check_accessibility zur Analyse der Webzugänglichkeit und simulate_colorblind zur Simulation von Farbenblindheit.

Werkzeug: check_accessibility

Überprüft die Erreichbarkeit einer bestimmten URL mithilfe von Axe-Core.

Parameter

  • url (erforderlich): Die zu analysierende URL

  • waitForSelector (optional): CSS-Selektor, auf den vor der Analyse gewartet werden soll

  • userAgent (optional): Benutzerdefinierter User-Agent-String für die Anfrage

Beispielverwendung

<use_mcp_tool>
<server_name>mcp-web-a11y</server_name>
<tool_name>check_accessibility</tool_name>
<arguments>
{
  "url": "https://example.com",
  "waitForSelector": ".main-content",
  "userAgent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
}
</arguments>
</use_mcp_tool>

Werkzeug: simulate_colorblind

Simuliert mithilfe von Farbmatrixtransformationen, wie eine Webseite Benutzern mit unterschiedlichen Arten von Farbenblindheit angezeigt wird.

Arten der Farbenblindheit

Das Tool unterstützt drei Arten der Farbenblindheitssimulation:

  1. Protanopie (Rotblindheit) – Verwendet Matrix:

    0.567, 0.433, 0
0.558, 0.442, 0
0, 0.242, 0.758

  2. Deuteranopie (Grünblindheit) – Verwendet Matrix:

    0.625, 0.375, 0
0.7, 0.3, 0
0, 0.3, 0.7

  3. Tritanopie (Blaublindheit) – Verwendet Matrix:

    0.95, 0.05, 0
0, 0.433, 0.567
0, 0.475, 0.525

Parameter

  • url (erforderlich): Die zu erfassende URL

  • type (erforderlich): Zu simulierender Typ der Farbenblindheit („Protanopie“, „Deuteranopie“ oder „Tritanopie“)

  • outputPath (optional): Benutzerdefinierter Pfad für die Screenshot-Ausgabe

  • userAgent (optional): Benutzerdefinierter User-Agent-String für die Anfrage

Beispielverwendung

<use_mcp_tool>
<server_name>mcp-web-a11y</server_name>
<tool_name>simulate_colorblind</tool_name>
<arguments>
{
  "url": "https://example.com",
  "type": "deuteranopia",
  "outputPath": "colorblind_simulation.png"
}
</arguments>
</use_mcp_tool>

Antwortformat

check_accessibility-Antwort

{
  "url": "analyzed-url",
  "timestamp": "ISO-timestamp",
  "violations": [
    {
      "impact": "serious|critical|moderate|minor",
      "description": "Description of the violation",
      "help": "Help text explaining the issue",
      "helpUrl": "URL to detailed documentation",
      "nodes": [
        {
          "html": "HTML of the affected element",
          "failureSummary": "Summary of what needs to be fixed"
        }
      ]
    }
  ],
  "passes": 42,
  "inapplicable": 45,
  "incomplete": 3
}

simulate_colorblind Antwort

{
  "url": "analyzed-url",
  "type": "colorblind-type",
  "outputPath": "path/to/screenshot.png",
  "timestamp": "ISO-timestamp",
  "message": "Screenshot saved with [type] simulation"
}

Fehlerbehandlung

Der Server umfasst eine umfassende Fehlerbehandlung für gängige Szenarien:

  • Netzwerkfehler

  • Ungültige URLs

  • Timeout-Probleme

  • Probleme mit der DNS-Auflösung

Fehlerantworten enthalten ausführliche Meldungen zur Unterstützung der Problemdiagnose.

Entwicklung

Projektstruktur

mcp-web-a11y/
├── src/
│   └── index.ts    # Main server implementation
├── build/          # Compiled JavaScript
├── output/         # Generated screenshots
├── package.json    # Project dependencies and scripts
└── tsconfig.json   # TypeScript configuration

Gebäude

npm run build

Dies wird:

  1. Kompilieren Sie TypeScript in JavaScript

  2. Machen Sie die Ausgabedatei ausführbar

  3. Platzieren Sie die kompilierten Dateien im build Verzeichnis

Debuggen

Der Server verfügt über eine detaillierte Debug-Protokollierung, die in der Konsolenausgabe angezeigt wird. Dazu gehören:

  • Netzwerkanfragen und -antworten

  • Seitenladestatus

  • Selektor-Wartestatus

  • Alle Konsolenmeldungen von der analysierten Seite

  • Fortschritt der Farbsimulation

Häufige Probleme und Lösungen

  1. Timeout-Fehler

    • Erhöhen Sie den Timeout-Wert im Code

    • Überprüfen der Netzwerkkonnektivität

    • Überprüfen Sie, ob die URL zugänglich ist

  2. DNS-Auflösungsfehler

    • Überprüfen Sie, ob die URL korrekt ist

    • Überprüfen der Netzwerkkonnektivität

    • Versuchen Sie es mit der Subdomäne www

  3. Selektor nicht gefunden

    • Überprüfen Sie, ob der Selektor auf der Seite vorhanden ist.

    • Warten Sie, bis der dynamische Inhalt geladen ist

    • Überprüfen Sie die Seitenquelle auf den richtigen Selektor

  4. Probleme mit der Farbsimulation

    • Stellen Sie sicher, dass die Farben der Seite in einem unterstützten Format (RGB, RGBA oder HEX) angegeben sind.

    • Prüfen Sie, ob die Seite dynamische Farbänderungen verwendet (möglicherweise ist zusätzliche Wartezeit erforderlich).

    • Überprüfen Sie, ob das Screenshot-Ausgabeverzeichnis vorhanden und beschreibbar ist.

Beitragen

  1. Forken Sie das Repository

  2. Erstellen eines Feature-Zweigs

  3. Übernehmen Sie Ihre Änderungen

  4. Push zum Zweig

  5. Erstellen einer Pull-Anforderung

Lizenz

Dieses Projekt ist unter der MIT-Lizenz lizenziert – Einzelheiten finden Sie in der Datei LICENSE .

Available Tools

2 tools
check_accessibilityC

Check web accessibility of a given URL using axe-core

ParametersJSON Schema
NameRequiredDescriptionDefault
urlYesURL to analyze
waitForSelectorNoOptional CSS selector to wait for before analysis
userAgentNoOptional user agent string to use for the request

TDQS

C2.9/5.0
Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states what the tool does but doesn't describe how it behaves: it doesn't mention whether this is a read-only analysis, what the output format might be, potential rate limits, authentication requirements, or error conditions. For a tool that performs web analysis, this leaves significant behavioral gaps.

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

Conciseness5/5

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

The description is a single, efficient sentence that communicates the core purpose without any wasted words. It's appropriately sized for a tool with a clear, focused function and is front-loaded with the essential information.

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

Completeness2/5

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

Given that there are no annotations and no output schema, the description should provide more complete context for this accessibility checking tool. It doesn't explain what kind of results to expect, what accessibility standards are checked, whether the analysis is comprehensive or limited, or how the tool handles dynamic content. For a tool with 3 parameters and no structured output documentation, this is insufficient.

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?

The input schema has 100% description coverage, so all parameters are documented in the schema itself. The description doesn't add any parameter-specific information beyond what's already in the schema descriptions. According to the scoring rules, when schema_description_coverage is high (>80%), the baseline is 3 even with no param info in the description.

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

Purpose4/5

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

The description clearly states the tool's purpose with a specific verb ('Check') and resource ('web accessibility of a given URL'), and mentions the technology used ('axe-core'). However, it doesn't explicitly differentiate from its sibling tool 'simulate_colorblind', which appears to be a related but distinct accessibility function.

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

Usage Guidelines2/5

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

The description provides no guidance on when to use this tool versus its sibling 'simulate_colorblind' or other alternatives. It doesn't mention prerequisites, typical use cases, or exclusions, leaving the agent with no contextual usage information beyond the basic purpose.

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

simulate_colorblindC

Simulate how a webpage looks for colorblind users

ParametersJSON Schema
NameRequiredDescriptionDefault
urlYesURL to capture
typeYesType of color blindness to simulate
outputPathNoOptional path to save the screenshot
userAgentNoOptional user agent string to use for the request

TDQS

C2.9/5.0
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It states the tool simulates colorblind views but doesn't describe how (e.g., generates a screenshot, modifies display, or returns data), what the output is (e.g., image file, visual report), or any behavioral traits like performance, rate limits, or side effects. This leaves significant gaps for an agent to understand the tool's operation.

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

Conciseness5/5

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

The description is a single, clear sentence: 'Simulate how a webpage looks for colorblind users.' It is front-loaded with the core purpose, has zero wasted words, and is appropriately sized for the tool's complexity. Every part of the sentence earns its place by conveying essential information efficiently.

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

Completeness2/5

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

Given the tool's moderate complexity (4 parameters, no output schema, no annotations), the description is incomplete. It lacks details on output (e.g., what is returned or saved), behavioral context (e.g., how simulation works, any limitations), and usage guidelines. While the schema covers parameters well, the description doesn't compensate for missing annotations or output schema, leaving the agent with insufficient context for effective use.

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?

The input schema has 100% description coverage, clearly documenting all four parameters (url, type, outputPath, userAgent) with details like enum values for 'type.' The description doesn't add any parameter-specific information beyond what the schema provides, such as explaining the simulation process or output format. Given the high schema coverage, a baseline score of 3 is appropriate as the schema handles the heavy lifting.

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

Purpose4/5

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

The description clearly states the tool's purpose: 'Simulate how a webpage looks for colorblind users.' It specifies the action (simulate) and resource (webpage appearance for colorblind users), making it easy to understand. However, it doesn't explicitly differentiate from its sibling tool 'check_accessibility,' which might also involve accessibility testing, though the focus here is specifically on colorblind simulation.

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

Usage Guidelines2/5

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

The description provides no guidance on when to use this tool versus alternatives. It doesn't mention the sibling tool 'check_accessibility' or any other tools, nor does it specify prerequisites, contexts, or exclusions. Usage is implied from the purpose but lacks explicit direction.

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

Tool Schema Changelog

Recent tool additions, removals, and schema changes observed during successful MCP inspections.

  1. 2 tool updates
    • First observedcheck_accessibility
    • First observedsimulate_colorblind
Deploy Server
Give agents eyes on the webHosted screenshot MCP. Send a URL, get a pixel-perfect image. $0.002 per grab. Works with Claude, Cursor, and Codex.grabbit.liveAd

TDQS

B3.1/5.0

Scored across 2 tools

Disambiguation5/5

The two tools have clearly distinct purposes: one checks general web accessibility using axe-core, while the other specifically simulates colorblindness effects on a webpage. There is no overlap or ambiguity between them.

Naming Consistency5/5

Both tools follow a consistent verb_noun pattern (check_accessibility, simulate_colorblind) with clear, descriptive names. The naming style is uniform and predictable throughout the set.

Tool Count2/5

With only two tools, the server feels thin for a web accessibility domain. While the tools are useful, typical accessibility testing involves more operations like checking screen reader compatibility, keyboard navigation, or ARIA attributes, suggesting notable gaps in coverage.

Completeness2/5

The tool set is severely incomplete for web accessibility. It lacks core operations such as validating HTML structure, testing screen reader output, assessing keyboard accessibility, or generating accessibility reports, which are essential for comprehensive accessibility evaluation.

Maintenance

ActivityInactive
ResponsivenessNo issues

Resources

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