SiteLint Auditor MCP Server

MCP server that runs SiteLint Auditor - WCAG and SiteLint Best Practices for accessibility, SEO, performance, and security audits via LLM agents.

The auditor bundle additionally supports WebMCP: when enabled it registers in-page tools on document.modelContext, so browser agents can run and inspect audits directly on a live site without this server. See WebMCP (in-page tools).

Quick start

npx @sitelint/auditor-mcp

Requires Chromium or Chrome. The MCP server automatically detects an installed system browser. If none is available, Puppeteer normally downloads Chrome during package installation; if that download was skipped, it downloads Chrome for Testing on the first audit. No browser path configuration is required.

Tools

audit_url

Audit a live URL.

{
  "url": "https://example.com",
  "standards": ["wcag"],
  "auditTypes": ["accessibility"],
  "wcagLevels": ["A", "AA"],
  "wcagVersions": ["2.2"],
  "wcagCriteria": []
}

audit_html

Audit raw HTML without fetching a URL. Defaults to waitUntil: "load" so image-based rules (e.g. oversized images, size calculations) see fully loaded assets. A timeout guards against hanging external resources — if the load event never fires, the audit aborts with a clear error instead of hanging. Pass waitUntil: "domcontentloaded" to skip slow assets entirely.

All filter parameters are required — pass empty arrays to skip a filter.

WCAG audit:

{
  "html": "<!DOCTYPE html><html>...</html>",
  "standards": ["wcag"],
  "auditTypes": ["accessibility"],
  "wcagLevels": ["A", "AA"],
  "wcagVersions": ["2.2"],
  "wcagCriteria": ["1.1.1", "1.4.3"]
}

SiteLint best practices (proprietary SEO, performance, security):

{
  "html": "<!DOCTYPE html><html lang=\"en\"><head><title>Test</title></head><body></body></html>",
  "standards": ["sitelint"],
  "auditTypes": ["seo", "performance", "security"],
  "wcagLevels": [],
  "wcagVersions": [],
  "wcagCriteria": []
}

Full audit (everything):

{
  "html": "<!DOCTYPE html><html>...</html>",
  "standards": ["wcag", "sitelint"],
  "auditTypes": ["accessibility", "performance", "security", "seo"],
  "wcagLevels": ["A", "AA", "AAA"],
  "wcagVersions": ["2.0", "2.1", "2.2"],
  "wcagCriteria": []
}

check_wcag_criterion

Check a single WCAG criterion against a URL.

{
  "url": "https://example.com",
  "criterion": "1.1.1"
}

Returns pass/fail with violation count.

Filter parameters

Filters are ANDed — a rule must match every provided filter to run. On audit_url filters are optional (omit or pass empty arrays to skip). On audit_html all filter parameters are required — pass empty arrays to skip.

| Parameter | Values | Example | | --- | --- | --- | | standards | wcag, sitelint | ["wcag"] | | auditTypes | accessibility, performance, security, seo | ["accessibility", "seo"] | | wcagLevels | A, AA, AAA, best_practices | ["A", "AA"] | | wcagVersions | 2.0, 2.1, 2.2 | ["2.2"] | | wcagCriteria | WCAG criterion numbers | ["1.1.1", "1.4.3"] |

Omit a parameter (or pass empty array) to skip that filter.

Resources

| URI | Description | | --- | --- | | auditor://standards | Supported WCAG criteria with levels | | auditor://report/{id} | Full JSON report from a previous audit |

Configuration

Environment variables

| Variable | Default | Description | | --- | --- | --- | | AUDITOR_BROWSER_PATH | Automatic detection | Optional custom Chromium/Chrome executable path | | AUDITOR_CONCURRENCY | 3 | Max concurrent audit pages (hard cap) | | AUDITOR_TIMEOUT | 30000 | Navigation/render timeout (ms) | | AUDITOR_HEADLESS | true | Set false to see browser | | AUDITOR_TRANSPORT | stdio | stdio or sse | | AUDITOR_PORT | 3100 | Port for SSE transport |

SSE / HTTP transport

Run the server over Streamable HTTP instead of stdio:

AUDITOR_TRANSPORT=sse AUDITOR_PORT=3100 npm start

The server listens on 127.0.0.1:3100 and accepts MCP requests via POST /. Host and Origin headers are validated (localhost only). Graceful shutdown on SIGINT/SIGTERM closes the browser and the HTTP server.

Client config:

{
  "mcpServers": {
    "sitelint-auditor": {
      "url": "http://127.0.0.1:3100"
    }
  }
}

CLI flags

auditor-mcp --bundle ./custom-bundle.js --timeout 60000 --headless false

| Flag | Env equivalent | | --- | --- | | --browser <path> | AUDITOR_BROWSER_PATH | | --concurrency <n> | AUDITOR_CONCURRENCY | | --timeout <ms> | AUDITOR_TIMEOUT | | --headless <bool> | AUDITOR_HEADLESS | | --bundle <path> | — | | --transport <stdio \| sse> | AUDITOR_TRANSPORT | | --port <n> | AUDITOR_PORT |

Integration guides

opencode

Add to ~/.config/opencode/opencode.json:

{
  "mcp": {
    "sitelint-auditor": {
      "type": "local",
      "command": ["npx", "-y", "@sitelint/auditor-mcp"]
    }
  }
}

For a local build:

{
  "mcp": {
    "sitelint-auditor": {
      "type": "local",
      "command": ["node", "/path/to/auditor-mcp/dist/cli.js"]
    }
  }
}

With custom Chromium:

{
  "mcp": {
    "sitelint-auditor": {
      "type": "local",
      "command": ["npx", "-y", "@sitelint/auditor-mcp"],
      "environment": {
        "AUDITOR_BROWSER_PATH": "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome",
        "AUDITOR_TIMEOUT": "60000"
      }
    }
  }
}

Claude Desktop

Edit claude_desktop_config.json:

{
  "mcpServers": {
    "sitelint-auditor": {
      "command": "npx",
      "args": ["-y", "@sitelint/auditor-mcp"]
    }
  }
}

Claude Code

Plugin (recommended)

/plugin marketplace add sitelint/auditor-mcp
/plugin install auditor-mcp@sitelint

Manual

claude mcp add sitelint-auditor -- npx -y @sitelint/auditor-mcp

Codex

Plugin (recommended)

codex plugin marketplace add sitelint/auditor-mcp
codex plugin add auditor-mcp@sitelint

Manual

codex mcp add sitelint-auditor -- npx -y @sitelint/auditor-mcp

ZCode

{
  "sitelint-auditor": {
    "type": "stdio",
    "command": "npx",
    "args": [
      "-y",
      "@sitelint/auditor-mcp@latest"
    ]
  }
}

VS Code (Cline)

In Cline extension settings → MCP Servers:

{
  "sitelint-auditor": {
    "command": "npx",
    "args": ["-y", "@sitelint/auditor-mcp"]
  }
}

VS Code (Continue)

In ~/.continue/config.json:

{
  "experimental": {
    "mcpServers": {
      "sitelint-auditor": {
        "command": "npx",
        "args": ["-y", "@sitelint/auditor-mcp"]
      }
    }
  }
}

AnythingLLM

{
  "mcpServers": {
    "sitelint-auditor": {
      "command": "npx",
      "args": ["-y", "@sitelint/auditor-mcp"]
    }
  }
}

Other MCP clients

Any MCP client can connect. Use stdio transport (default) for local tools, or AUDITOR_TRANSPORT=sse with AUDITOR_PORT=3100 for remote.

Build from source

git clone <repo>
cd auditor-mcp
npm install
npm run build

# Bundle the auditor engine
cp /path/to/auditor/dist/auditor.bundle.js vendor/
cp /path/to/auditor/app/translations/en-us.json vendor/translations/

Requirements

• Node.js 20+
• Chromium or Chrome (detected automatically, or downloaded by Puppeteer during installation/on the first audit if needed)
• SiteLint Auditor bundle (vendored as vendor/auditor.bundle.js)

How it works

1. Launches headless Chromium via Puppeteer (single browser, pages capped by AUDITOR_CONCURRENCY)
2. Loads the target page and waits for it to settle (bounded by AUDITOR_TIMEOUT)
3. Injects the SiteLint Auditor JS bundle into the page
4. Runs a single-shot audit against the current DOM state
5. Formats results into a concise text report with grouping and truncation for long outputs
6. Stores full JSON as a resource accessible via auditor://report/{id}

Navigation failures, timeouts, and browser-launch errors are returned as readable messages rather than raw exceptions.

Limitations vs. embedded auditor

When SiteLint Auditor is embedded directly into a website via <script>, it watches for DOM mutations, re-tests dynamically loaded content, and provides an interactive sidebar UI. The MCP server does not do any of that — it takes a one-time snapshot of the page at the moment of injection. Content loaded after the audit starts (lazy images, infinite scroll, SPA route transitions) is not evaluated. For SPAs or pages with heavy dynamic content, consider waiting for full render before calling the tool.

WebMCP (in-page tools)

WebMCP turns the page itself into a tool server: the site exposes client-side functions with JSON schemas, and a browser agent invokes them directly in the open tab. No stdio/SSE transport, no headless browser, no server deployment.

When the auditor is embedded via <script> with the webmcp option enabled, it registers:

| Tool | Description | | --- | --- | | sitelint_run_audit | Runs a full audit of the live page; returns score and issue totals | | sitelint_get_reports | Issues from the last audit with translated messages and element locators (jsPath, cssSelector, xpath); filters ruleId, severity, standard; paginated via offset/limit (default 25, max 100) | | sitelint_list_rules | All registered rules with id, severity, standard and WCAG level | | sitelint_highlight_issue | Scrolls to and visually highlights the element for an issue jsPath returned by sitelint_get_reports |

Enabling from page code:

auditor.config({ webmcp: true });
auditor.run();

The flag is opt-in and defaults to false. Registration is feature-detected: browsers without document.modelContext silently skip it and the auditor behaves exactly as before.

When to use WebMCP instead of this server

• Live page state — audits SPAs, authenticated views, and content rendered after load; the server only snapshots the initial DOM (see Limitations vs. embedded auditor above).
• Fix-and-verify loop — the agent changes the page, re-runs sitelint_run_audit, and uses sitelint_highlight_issue to show the user what remains — all inside the user's tab.
• Assistive and browser-agent workflows — the agent and the user share one context.

Requirements

• Chromium 146+ with WebMCP enabled (chrome://flags/#enable-webmcp-testing in preview builds; Chrome 150+ exposes the producer API on document.modelContext)
• Secure context (HTTPS)
• Tools are visible to same-origin consumers only; cross-origin exposure requires the tools permissions policy plus exposedTo at registration

WebMCP complements this server rather than replacing it: headless audits of arbitrary URLs (CI, batch checks, sites that do not embed the auditor) stay on @sitelint/auditor-mcp; in-browser agents driving a live site use the WebMCP tools.