WSG Check MCP server

WSG-Check

Check a website against automated heuristics based on the W3C Web Sustainability Guidelines. Get a weighted score, recommendations, and reports in terminal, JSON, Markdown, or HTML format through a CLI or a Next.js web app.

Release status

The latest release is v0.6.0. <!-- x-release-please-version -->

It targets WSG July-2026 (Group Note Draft). It includes an MCP server for AI assistants, with the checkurl, listguidelines, and get_guideline tools, listed in the MCP Registry as io.github.ivanoats/wsg-check. The server first shipped in v0.4.0; v0.3.0 was tagged on GitHub but not published to npm. See the changelog and spec versioning policy.

Scores from different spec versions should not be treated as directly comparable. The package version and check selection also matter when comparing reports.

Quick start

Requires Node.js 22 or later. Pin the released CLI for reproducible usage:

npx @sustainablewebsites/wsg-check@0.6.0 https://example.com # x-release-please-version

# Or install globally
npm install -g @sustainablewebsites/wsg-check@0.6.0 # x-release-please-version
wsg-check https://example.com --format json --output report.json

To run the current source, including unreleased features, use Node.js 22.22.1 or later (required by development tooling):

git clone https://github.com/ivanoats/wsg-check.git
cd wsg-check
npm ci             # prepare also generates Panda CSS tokens
npm run dev        # http://localhost:3000

# Build and run the CLI from this checkout
npm run build:cli
node dist/cli/index.js https://example.com

See CONTRIBUTING.md for environment configuration and development commands.

What the results mean

• Checks cover web development, UX, and hosting. The business category has no automated checks.
• Analysis uses fetched HTML and HTTP metadata; it does not render JavaScript, measure Core Web Vitals, or download every referenced asset.
• CO₂ estimates use HTML bytes and the SWD v4 model, not measured full-page energy consumption. Failed green-hosting lookups fall back to false.
• Report page weight is the HTML document size; resource and third-party counts come from references in the HTML. Referenced assets are not downloaded or measured.
• Security headers, form validation, native form features, and image alternative text remain visible as related checks, excluded from WSG scores.

CLI Usage

WSG-Check ships with a command-line tool that lets you check any website directly from your terminal or integrate checks into CI pipelines.

Basic usage

# Check a website with default (terminal) output
npx @sustainablewebsites/wsg-check https://example.com

# Output as JSON
npx @sustainablewebsites/wsg-check https://example.com --format json

# Save the report to a file
npx @sustainablewebsites/wsg-check https://example.com --format markdown --output report.md

# Fail the process (exit 1) if the score is below 70
npx @sustainablewebsites/wsg-check https://example.com --fail-threshold 70

Options

Shortened. The full README is on GitHub.