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Web Accessibility MCP Server

by bilhasry-deriv
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Веб-доступность MCP-сервера

значок кузнеца

Сервер MCP (Model Context Protocol), предоставляющий возможности анализа веб-доступности с использованием axe-core и Puppeteer.

Функции

  • Анализ веб-доступности любого URL с помощью axe-core

  • Имитация цветовой слепоты (протанопии, дейтеранопии, тританопии) с использованием цветовых матриц

  • Подробные отчеты о нарушениях доступности

  • Поддержка пользовательских агентов и селекторов

  • Отладочное ведение журнала для устранения неполадок

  • Комплексные проверки доступности на основе рекомендаций WCAG

Related MCP server: Cursor A11y MCP

Предпосылки

  • Node.js (v14 или выше)

  • нпм

Установка

Установка через Smithery

Чтобы автоматически установить сервер веб-доступности MCP для Claude Desktop через Smithery :

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

Ручная установка

  1. Клонируйте репозиторий:

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

  1. Установить зависимости:

npm install

  1. Сборка сервера:

npm run build

Конфигурация

Добавьте сервер в файл настроек MCP (обычно он находится по адресу ~/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"
      }
    }
  }
}

Переменные среды

  • MCP_OUTPUT_DIR : Каталог, в котором будут сохраняться результаты снимков экрана.

    • Требуется для инструмента simulate_colorblind

    • Если не указано, по умолчанию используется «./output» относительно текущего рабочего каталога.

    • При настройке в настройках MCP должен быть указан абсолютный путь.

Использование

Сервер предоставляет два инструмента: check_accessibility для анализа доступности веб-сайтов и simulate_colorblind для моделирования дальтонизма.

Инструмент: check_accessibility

Проверяет доступность указанного URL-адреса с помощью axe-core.

Параметры

  • url (обязательно): URL для анализа

  • waitForSelector (необязательно): селектор CSS, которого следует ожидать перед анализом

  • userAgent (необязательно): Пользовательская строка агента пользователя для запроса

Пример использования

<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>

Инструмент: simulation_colorblind

Имитирует то, как веб-страница выглядит для пользователей с различными типами дальтонизма, используя преобразования цветовой матрицы.

Типы дальтонизма

Инструмент поддерживает три типа моделирования дальтонизма:

  1. Протанопия (слепота к красному цвету) - Использует матрицу:

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

  2. Дейтеранопия (зеленая слепота) — использует матрицу:

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

  3. Тританопия (сине-слепота) — использует матрицу:

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

Параметры

  • url (обязательно): URL для захвата

  • type (обязательно): Тип дальтонизма для имитации («протанопия», «дейтеранопия» или «тританопия»).

  • outputPath (необязательно): Пользовательский путь для вывода скриншота.

  • userAgent (необязательно): Пользовательская строка агента пользователя для запроса

Пример использования

<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>

Формат ответа

check_accessibility Ответ

{
  "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
}

симулировать_дальтонизм Ответ

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

Обработка ошибок

Сервер включает в себя комплексную обработку ошибок для распространенных сценариев:

  • Ошибки сети

  • Недействительные URL-адреса

  • Проблемы с тайм-аутом

  • Проблемы с разрешением DNS

Ответы об ошибках будут включать подробные сообщения, которые помогут диагностировать проблему.

Разработка

Структура проекта

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

Здание

npm run build

Это позволит:

  1. Компилировать TypeScript в JavaScript

  2. Сделать выходной файл исполняемым

  3. Поместите скомпилированные файлы в каталог build

Отладка

Сервер включает в себя подробное отладочное логирование, которое можно наблюдать в выводе консоли. Это включает в себя:

  • Сетевые запросы и ответы

  • Статус загрузки страницы

  • Статус ожидания селектора

  • Любые консольные сообщения с анализируемой страницы

  • Прогресс моделирования цвета

Распространенные проблемы и решения

  1. Ошибки тайм-аута

    • Увеличьте значение тайм-аута в коде

    • Проверьте сетевое подключение

    • Убедитесь, что URL доступен.

  2. Ошибки разрешения DNS

    • Проверьте правильность URL-адреса.

    • Проверьте сетевое подключение

    • Попробуйте использовать поддомен www

  3. Селектор не найден

    • Убедитесь, что селектор существует на странице.

    • Дождитесь загрузки динамического контента.

    • Проверьте исходный код страницы на наличие правильного селектора.

  4. Проблемы с симуляцией цвета

    • Убедитесь, что цвета страницы указаны в поддерживаемом формате (RGB, RGBA или HEX)

    • Проверьте, использует ли страница динамическую смену цветов (может потребоваться дополнительное время ожидания)

    • Убедитесь, что выходной каталог скриншота существует и доступен для записи.

Внося вклад

  1. Форк репозитория

  2. Создать ветку функций

  3. Примите ваши изменения

  4. Нажмите на ветку

  5. Создать запрос на извлечение

Лицензия

Данный проект лицензирован по лицензии MIT — подробности см. в файле 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

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