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seo-meta-onpage (M7)

Head hygiene is cheap, deterministic, and the first thing every crawler reads. Reference: references/schema-tier1.md for the structured-data layer that sits alongside the head (owned by M5).

Inputs

Work from the PageSnapshot named in your dispatch envelope: read parsed from <run_dir>/pages/<slug>.json (title, metas[], robots_meta[], canonicals[], word_count) plus headers (content-language, x-robots-tag); Grep pages/<slug>.html for verbatim evidence; site artifacts live in <run_dir>/site/{robots.json,sitemaps.json,discovery.json}. Deterministic findings already emitted by audit.mjs are listed in <run_dir>/findings.deterministic.json — do not re-emit those ids; add model-judged findings only. If invoked directly with a URL/path and no snapshot exists, first run node "${CLAUDE_PLUGIN_ROOT}/scripts/snapshot.mjs" <target> --out "${CLAUDE_PLUGIN_DATA}/runs" and use the printed snapshot path.

Audits

Working from the PageSnapshot (parsed_rendered when render.used is not none, else parsed):

1. Title — exactly one <title>. Length is judged against the shared bands in scripts/lib/bands.mjs (the single source; parse-html.mjs, the on-page checks and this skill all read it): pass 30-60 characters, recommended 50-60. Inside 50-60 the verdict is recommended; inside 30-60 but outside that, pass; below 30 short, above 60 long — both are warn, never fail. Fail only when the title is missing or empty, or duplicated site-wide across distinct URLs. Not all caps; not a pure keyword list.
2. Meta description — present, judged against the same shared bands: pass 70-160 characters, recommended 150-160. Outside the pass band is warn, never fail — Google rewrites descriptions freely. Not duplicated site-wide; describes this page, not boilerplate.
3. Viewport — <meta name="viewport" content="width=device-width, initial-scale=1"> present (fail if missing — mobile rendering/indexing depends on it).
4. Charset — <meta charset="utf-8"> present and in the first 1024 bytes of <head>.
5. Language — <html lang="…"> present and a valid BCP-47 tag.
6. Robots meta — sanity-check <meta name="robots">: flag an accidental noindex/nofollow on a page meant to rank. Full indexability/canonical logic (including the canonical tag) is owned by seo-indexability (M2) — here only note presence of <link rel="canonical">, do not adjudicate it.

Fixes

• AUTO — add missing viewport, charset (utf-8), and <html lang> (inferred from Content-Language header or page text; leave a TODO if ambiguous). These are deterministic, additive, verifiable writes → diff for fix.
• PROPOSED — generate/trim a <title> and meta description from <h1>, lead paragraph, and primary topic: length-bounded, keyword-aware but not stuffed, brand suffix only if the site uses one. Each is a draft requiring per-item accept (humans own messaging).
• ADVISORY — removing an intentional noindex is never auto-written; surface it and let the user decide.
• Never fabricate a title, description, or lang — when content is too thin to derive a value, leave a clearly-marked TODO: placeholder for the user to fill.

Verification

• Method dom_assert: node "${CLAUDE_PLUGIN_ROOT}/scripts/parse-html.mjs" --snapshot <pages/<slug>.json> (or --url <u> / --file <path>) — returns title (value/length/ok), meta_description (value/length/ok), robots_meta, canonical, and head_hygiene (viewport/charset/lang) so each head element's presence and length is asserted directly against the snapshot.
• Duplicate-title/description checks need the full crawl set; when only a single page is available the cross-URL assertion is reported needs_api, never a false pass.

Findings

Findings conform to schema/finding.schema.json. Severity policy: 5 is reserved for catastrophic, eligibility-killing facts at site/template scope; 4 major · 3 moderate · 2 minor · 1 cosmetic · 0 informational — and only an established severity-5 fail in an active category can cap a score (references/scoring-model.md). Head hygiene never reaches 5. Examples:

• M7.title.missing — no <title> (fail, severity 3, fixable: proposed, axis search, confidence established).
• M7.title.length_out_of_band — title 78 chars, outside the 30-60 pass band and likely truncated in the SERP (warn, severity 3, fixable: proposed, axis search, confidence directional). Quote the length and the band that produced the verdict.
• M7.description.length_out_of_band — description outside the 70-160 pass band (warn, severity 2, fixable: proposed, axis search, confidence directional).
• M7.viewport.missing — no responsive viewport (fail, severity 3, fixable: auto, axis search, confidence established).
• M7.title.duplicate_across_urls — the same <title> is served from several sampled URLs (warn, severity 3, fixable: proposed, axis search, confidence directional). One finding per duplicate cluster, quoting the shared title and the URLs.
• M7.description.duplicate_across_urls — the same meta description is served from several sampled URLs (warn, severity 2, fixable: proposed, axis search, confidence directional).

Both duplicate checks are cross-URL: with fewer than two content pages in the run they are reported once as M7.title.duplicate_across_urls with status needs_api (severity 0, unscored), never as a pass. Platform-conditional ids. This module also emits 6 ids that fire only when profile.json names the platform (shopify, wordpress, nextjs, gatsby, jekyll, react-router). They are indexed in references/routing.md § Platform-conditional finding ids and specified in references/platforms/<id>.md §10.

Each finding: evidence.observed quotes the head verbatim (e.g. the exact title string + its length); verification.reproduce is the runnable parse-html.mjs command above; expected_impact is banded + confidence-tagged (no naked %).

Honesty

• The "meta keywords" tag is dead — Google ignores it; do not add or recommend it.
• Title/description length bands are SERP-display heuristics (Google truncates on pixel width, not characters), not ranking factors — out-of-band values are warn, never fail, and impact is directional at most. The pass band is deliberately wider than the recommended band so a 35-character title is not reported as a defect; both bands come from scripts/lib/bands.mjs so the script, the report, and this skill can never disagree.
• Google frequently rewrites the displayed title/description from on-page content; a perfect tag is not guaranteed to appear, so never promise a SERP snippet as a ranking gain.