Agent skill

seo-checker

Audit web pages for SEO issues in a real browser. Checks rendered meta tags, heading hierarchy, image alt text, structured data, canonical URLs, mobile rendering, and performance signals. Produces a scored report with specific findings and fixes. Read-only — inspects, doesn't modify. Requires the hanzi browser automation MCP server and Chrome extension.

View SKILL.md on GitHub Repository
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Install this agent skill to your Project

npx add-skill https://github.com/hanzili/hanzi-browse/tree/main/server/skills/seo-checker

SKILL.md

SEO Checker

You audit web pages for SEO issues using a real browser — rendered meta tags, actual heading structure, real schema markup, mobile viewport behavior. This skill is read-only: observe and report, don't modify.

Tool Selection Rule

  • Prefer existing tools first (code search, local files, curl). Review HTML source, meta tags, and sitemap before opening the browser.
  • Use Hanzi for Phase 2–5 — always open the browser for these phases even if Phase 1 found all static data. Do not substitute curl or WebFetch for browser phases.

Before Starting

Call browser_status to verify the extension is reachable. If unavailable, tell the user to install from: https://chromewebstore.google.com/detail/hanzi-browse/iklpkemlmbhemkiojndpbhoakgikpmcd

What You Need

  1. URL — page or site to audit
  2. Scope — single page, specific section, or full site (default: single page)
  3. Focus — any specific SEO concerns (e.g., "we're not showing up in rich results", "mobile traffic dropped")

Audit Phases

Phase 1 — Source Review (before browser)

Check what you can without a browser:

  • Robots.txt: Fetch <domain>/robots.txt — check for accidental Disallow: / or blocked important paths. Note: some sites serve different robots.txt to different user agents (UA sniffing). If the curl result looks suspicious or overly restrictive, verify with browser_start to see what a real browser receives.
  • Sitemap: Fetch <domain>/sitemap.xml — verify it exists and includes the target URL
  • HTML source: If accessible, review raw <head> for meta tags, canonical, hreflang
  • Codebase (if source available): Scan for hardcoded noindex, missing meta tag templates, SEO component patterns

Summarize findings before opening the browser.

Phase 2 — Meta & Head Tags (browser)

Use browser_start to open the page and inspect the rendered DOM. JavaScript-rendered SPAs may have different meta tags than the raw HTML source.

  • Title tag: Exists, 50-60 characters, unique, descriptive (not "Home" or "Untitled")
  • Meta description: Exists, 150-160 characters, includes target keywords, compelling for CTR
  • Canonical URL: Present, points to the correct URL (not a duplicate or wrong domain)
  • Robots meta: Check for unintentional noindex, nofollow, or none directives
  • Open Graph tags: og:title, og:description, og:image, og:url — all present and correct
  • Twitter Card tags: twitter:card, twitter:title, twitter:description, twitter:image
  • Viewport meta: <meta name="viewport" content="width=device-width, initial-scale=1"> present
  • Charset & lang: <meta charset="utf-8"> and <html lang="..."> set correctly

Screenshot the page after loading.

Phase 3 — Content Structure (browser)

  • H1 tag: Exactly one per page, descriptive, contains primary keyword
  • Heading hierarchy: H1 → H2 → H3 — no skipped levels (e.g., H1 → H3 with no H2)
  • Image alt text: All meaningful images have descriptive alt text; decorative images use alt=""
  • Internal links: Key pages are linked, anchor text is descriptive (not "click here")
  • Broken links: Check for obvious 404s or dead links on the page

Phase 4 — Structured Data (browser)

  • JSON-LD / Microdata: Check <script type="application/ld+json"> blocks in the rendered DOM
  • Schema types: Verify appropriate types are used (Article, Product, LocalBusiness, BreadcrumbList, FAQ, etc.)
  • Required properties: Each schema type has required fields — check they're populated (e.g., Article needs headline, datePublished, author)
  • Validation: Flag malformed JSON-LD or schemas with empty/placeholder values

Phase 5 — Mobile & Performance (browser)

Render the page at a mobile viewport (375×812, iPhone-sized):

  • Mobile layout: No horizontal scrolling, text readable without zooming, tap targets at least 48×48px
  • Content parity: Mobile version has the same key content as desktop (Google uses mobile-first indexing)
  • Image optimization: Check for oversized images (e.g., 2000px wide image in a 375px container), missing loading="lazy" on below-fold images
  • CLS indicators: Elements that visibly shift during load (ads, images without dimensions, dynamically injected content)
  • Core Web Vitals: Use javascript_tool to extract real navigation timing from the Performance API:
javascript
const nav = performance.getEntriesByType('navigation')[0];
const paint = performance.getEntriesByType('paint');
({
  ttfb: nav.responseStart - nav.requestStart,
  domContentLoaded: nav.domContentLoadedEventEnd - nav.startTime,
  load: nav.loadEventEnd - nav.startTime,
  fcp: paint.find(e => e.name === 'first-contentful-paint')?.startTime,
});

Screenshot at mobile viewport.

Scoring

Rate each category on a 0-10 scale:

Category What's checked
Meta Tags Title, description, canonical, robots, OG, Twitter cards
Content Structure H1, heading hierarchy, image alt text, internal links
Structured Data JSON-LD presence, correct types, required properties
Mobile Responsive layout, content parity, tap targets
Performance Signals Image sizes, lazy loading, CLS indicators
Internationalisation hreflang alternates, lang attribute, multilingual implementation

Overall score = average of the 6 category scores (out of 10).

  • 9-10: Excellent — production-ready SEO
  • 7-8: Good — minor improvements needed
  • 5-6: Needs work — several issues affecting visibility
  • 3-4: Poor — significant SEO problems
  • 0-2: Critical — major issues blocking indexing or ranking

Report Format

# SEO Audit: [URL]
Overall Score: [X]/10

## Meta Tags — [X]/10
✓ [What passed — one line each]
✗ [What failed — element, issue, specific fix]
  📸 Screenshot: [evidence]

## Content Structure — [X]/10
✓ / ✗ [same format]

## Structured Data — [X]/10
✓ / ✗ [same format]

## Mobile — [X]/10
✓ / ✗ [same format]

## Performance Signals — [X]/10
✓ / ✗ [same format]

## Internationalisation — [X]/10
✓ / ✗ [same format]

## Top 3 Priorities
1. [Most impactful fix — what to do and why]
2. [Second priority]
3. [Third priority]

For each failing item, include:

  • What's wrong: specific element and current value
  • Why it matters: impact on search visibility or user experience
  • How to fix: concrete action (e.g., "Add <meta name="description" content="..."> with 150-160 chars describing the page")
  • Reference: link to relevant Google/web.dev guideline where helpful

Rules

  • One page at a time — screenshot at each phase
  • Be specific: "the hero image (1920×1080, 2.4MB)" not "some images are large"
  • Cite standards: Google's SEO guidelines, web.dev, Schema.org specs
  • Don't report unverified issues — if the rendered DOM differs from source, note both
  • If browser_start times out, call browser_screenshot to diagnose
  • Read-only — never modify the page, submit forms, or click CTAs
  • SPA handling: always check rendered DOM, not just HTML source — SPAs may inject meta tags via JavaScript

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