Astro SEO

Astro SEO

Audits and improves the SEO setup of an Astro site against the full stack described in Astro SEO: the definitive guide. The skill covers nine areas — technical foundation, structured data, content, site structure, performance, sitemaps and indexing, agent discovery, redirects, and analytics — and produces drop-in code for anything missing or weak.

The opinionated spine of this skill is @jdevalk/astro-seo-graph. Most of the fixes route through it. If the project doesn't use it yet, installing it is the first recommendation.

Code recipes live in AGENTS.md — read it when you need to implement a specific fix. This file has the workflow and audit checklist.

Workflow

1. Detect the project — confirm this is an Astro site and understand its shape.
2. Audit — score nine categories and produce actionable findings.
3. Improve — generate or modify files to close the gaps. Recipes are in AGENTS.md.
4. Metadata pass — invoke metadata-check on every short string the skill generated (titles, descriptions, schema description fields, FAQ answers, frontmatter excerpts).
5. Verify — run the build, check validations pass, remind the user about non-file tasks (Search Console, Bing Webmaster Tools, IndexNow key verification).

Phase 0: Detect the project

Confirm the basics before auditing:

• astro.config.mjs / astro.config.ts exists.
• package.json has astro as a dependency.
• site: is set in astro.config — canonicals, sitemaps, and OG image URLs all derive from this. If it's missing, empty, or http://localhost, flag it as a blocking issue before anything else. This is the single most common misconfiguration.
• Content collections in src/content/ (or legacy src/pages/ markdown).
• Deployment target — read package.json, vercel.json, netlify.toml, wrangler.toml, or public/_headers to determine the host. This drives redirect and header syntax in Phase 2.
• Is @jdevalk/astro-seo-graph already installed? If yes, record the version and which features are wired (grep for <Seo, seoGraph(, createSchemaEndpoint, createSchemaMap, FuzzyRedirect, createIndexNowKeyRoute, createMarkdownEndpoint, createApiCatalog, gitLastmod). Check the installed version against the latest on npm with npm view @jdevalk/astro-seo-graph version. If the project is behind, recommend an upgrade in Phase 2 before auditing feature gaps — the package ships new defaults and fixes regularly, and an outdated version is a plausible cause for any audit finding. Phase 2 branches on this.
• Is the site multilingual? Check for i18n in astro.config or multiple locale directories under src/content/. If yes, hreflang matters; if no, skip it.

Ask only what you can't detect. Don't ask the user what the site is about — read astro.config.mjs and the homepage content.

Phase 1: Audit

Score each category out of 10. For each, give 2–4 specific findings that quote the actual code or config. Within each category, checks are tiered:

• Must — ship blockers. A failure here causes visible SEO regression.
• Should — standard practice. Skipping costs reach.
• Nice — forward-looking or situational. Useful but not baseline for every site.

Skip Nice checks for small personal blogs unless the user asks for the full treatment.

1. <Seo> component and head metadata (/10)

• Must — single component for all head metadata (not scattered across layouts).
• Must — site: in astro.config is set to the production origin.
• Must — canonical URLs derived from site config with tracking params stripped.
• Must — canonical omitted when noindex is true (per Google's recommendation).
• Must — fallback chain for missing SEO fields: seo.title → title → siteName; seo.description → excerpt → first paragraph. Pages with blank titles or descriptions are the most common symptom of a broken fallback.
• Should — robots meta includes max-snippet:-1, max-image-preview:large, max-video-preview:-1.
• Should — Twitter tags suppressed when they duplicate Open Graph (Twitter falls back automatically).
• Should — hreflang alternates present on multilingual sites. Skip if monolingual.
• Nice — uses @jdevalk/astro-seo-graph's <Seo> component rather than hand-rolled. (Hand-rolled that covers everything above is fine; this skill nudges toward the package because it handles the fallback chain and robots rules by default.)

2. Structured data / JSON-LD graph (/10)

• Single flat Article object, or a linked @graph with multiple entities?
• Entities wired with @id references?
• WebSite, Blog/WebPage, Person/Organization, BlogPosting/Article, BreadcrumbList, ImageObject all present where relevant?
• Trust signals: publishingPrinciples, copyrightHolder, copyrightYear, knowsAbout, SearchAction?
• Validates in Rich Results Test and ClassySchema?

3. Content collections and SEO schema (/10)

• Content collections defined with Zod schemas?
• seoSchema from @jdevalk/astro-seo-graph enforcing title (5–120) and description (15–160) lengths?
• Required fields (publishDate, title, excerpt) enforced at build time?
• Markdown-stripped articleBody exposed in schema endpoints (up to 10K chars)?

4. Open Graph images (/10)

• Every page has an OG image, or many missing?
• 1200×675 (Google Discover minimum 1200px wide, 16:9 ratio)?
• Generated at build time via satori + sharp, or manual?
• JPEG (social platforms don't reliably support WebP/AVIF)?
• Route derives OG URL from the slug automatically?
• Every <img> in rendered HTML has an alt attribute (or alt="" / role="presentation" for decorative images)? validateImageAlt on seoGraph() catches this at build time in ≥ 1.1.0.

5. Sitemaps and indexing (/10)

• Must — @astrojs/sitemap installed, sitemap index reachable.
• Must — robots.txt references the sitemap index.
• Must — RSS feed exists (@astrojs/rss), advertised via <link rel="alternate" type="application/rss+xml">, contains full post content (not truncated excerpts).
• Should — split per-collection via chunks option (sitemap-posts-0.xml, etc.) — much easier to debug indexing in GSC.
• Should — lastmod populated from git commit timestamps, not frontmatter dates or CI file timestamps. @jdevalk/astro-seo-graph ≥ 1.4.0 exports gitLastmod(filePath, { excludeCommits, depth }) for this — it returns the committer date of the most recent non-excluded commit that touched the file, or null if git is unavailable. Wire it into the sitemap serialize callback. If the codebase has a hand-rolled execSync('git log ...') helper, replace it with the package export — the export handles bulk-commit exclusion (imports, reformats) which a naïve -1 lookup can't.
• Should — IndexNow integrated and submitting on each build, with key verification route at /[key].txt. ≥ 1.0.1 excludes /404 from submissions by default. Gate submission on the production host (e.g. process.env.CF_PAGES === '1' && CF_PAGES_BRANCH === 'main', VERCEL_ENV === 'production', CONTEXT === 'production'). Unconditional submission pings the endpoint on every local npm run build and preview deploy with URLs the production host hasn't served yet, which gets the key marked invalid (403) and forces rotation.

6. Agent discovery (/10)

• Should — schema endpoints (/schema/*.json) exposing corpus-wide JSON-LD.
• Should — schema map (/schemamap.xml) listing all endpoints, with Schemamap: directive in robots.txt.
• Should — llms.txt at the site root listing pages (title + description) for LLM consumers. @jdevalk/astro-seo-graph ≥ 0.9.0 generates this via the llmsTxt integration option.
• Should — markdown-alternate URLs (/blog/post.md next to /blog/post/) serving clean markdown with YAML frontmatter for AI agents to consume without HTML parsing. @jdevalk/astro-seo-graph ≥ 1.2.0 ships createMarkdownEndpoint for the route and a markdownAlternate: true integration option that emits <link rel="alternate" type="text/markdown"> on every page. ≥ 1.3.0 adds post-build verification: the integration walks the build output and strips any link whose .md target isn't on disk (with a warn per occurrence) — so a misconfigured endpoint surfaces as a build warning instead of a shipped 404. Pair with a Cloudflare Transform Rule (URL rewrite via wildcard_replace, no Vary: Accept header — CF strips custom Vary values) for content negotiation on Accept: text/markdown without needing SSR.
• Should — API catalog at /.well-known/api-catalog per RFC 9727. @jdevalk/astro-seo-graph ≥ 1.4.0 ships createApiCatalog, which auto-types schema endpoints to their https://schema.org/<Type> URLs and absolutizes paths against siteUrl. List the schema endpoints, schemamap, and any site-specific APIs (/ask, /feed.xml, etc.). The RFC is finalized so the format is stable; adoption is early but the cost is one route file.
• Should — Content Signals directive in robots.txt (e.g. Content-Signal: ai-train=yes, search=yes, ai-input=yes). Declares preferences for AI training, search grounding, and AI input use independently of crawl access. The spec is an IETF draft and adoption is early, but it's one line in a file every site already has.
• Should — Link header on /* pointing to discovery files (sitemap, llms.txt, api-catalog, schemamap, and any MCP / A2A cards the site publishes). Agents reading response headers find them without parsing HTML. On Cloudflare Pages / Netlify this is public/_headers; on Vercel it's vercel.json.
• Nice — MCP server card at /.well-known/mcp/server-card.json (SEP-1649) and / or A2A agent card at /.well-known/agent-card.json (A2A protocol). Only relevant when the site actually exposes an MCP server or A2A agent. Both are static JSON files declaring the endpoint, capabilities, and skills. Skip otherwise.
• Nice — <link rel="nlweb"> pointing to a conversational endpoint. NLWeb is early; the tag is one line and worth having, but it's not a scoring blocker in 2026.
• Nice — ARD (Agentic Resource Discovery) catalog at /.well-known/ai-catalog.json, listing what the domain offers (MCP server, A2A agent, OKF bundle, site-specific APIs). v0.9 draft, so optional — but it's the discovery layer the MCP / A2A cards and OKF bundle pay off through. Two gotchas: the base spec (Agent-Card/ai-catalog) names the media-type field mediaType while the ARD layer (ards-project/ard-spec) names it type — emit both keys with the same value so the entry validates under either reading (both specs require consumers to ignore unknown keys). ARD also adds an optional representativeQueries array of sample prompts per entry.
• Nice — OKF (Open Knowledge Format) bundle: a tree of typed Markdown concept files (one per page, paths mirroring canonical URLs) packaged as a single .tar.gz, with index files in between. Serving and discovery are explicit non-goals of OKF — that's what the ARD catalog entry is for. v0.9 draft, optional. There's no registered media type yet, so the interim string is application/okf-bundle+gzip (tracked in knowledge-catalog#111 and ard-spec#27); mark it interim, it may change. Best generated as one more output of an existing content pipeline rather than a hand-maintained copy.

7. Performance (/10)

• Static output by default (no SSR on pages that don't need it)?
• Zero client-side JS unless an island requires it?
• Astro <Image> component used for all content images (responsive srcset, WebP, lazy, async)?
• Primary web font preloaded in woff2?
• <ClientRouter /> with defaultStrategy: 'viewport' for prefetch?
• Hashed assets under /_astro/ serve Cache-Control: public, max-age=31536000, immutable?
• No-Vary-Search response header stripping UTM parameters from cache key?

8. Redirects and error handling (/10)

• public/_redirects (or equivalent) maintained for every URL that ever existed and moved?
• 301 not 302 for permanent moves?
• FuzzyRedirect component from @jdevalk/astro-seo-graph wired into the 404 page?
• 404 page itself returns a 404 status, not 200?

9. Build-time validation and content quality (/10)

• Must — seoGraph() integration running on each build with validateH1 and validateUniqueMetadata enabled. For JSON-LD validation, pass warnOnDanglingReferences: true to assembleGraph() in seo-graph-core — that's the assembly-time check, not an integration option.
• Should — validateImageAlt, validateMetadataLength, and validateInternalLinks enabled on seoGraph() (all default true in ≥ 1.1.0). They catch missing alt text, titles or descriptions outside SERP bounds (defaults: title 30–65, description 70–200), and internal links that 404 or hit a trailing-slash mismatch. Upgrade to ≥ 1.1.1 if the project is on 1.1.0 — that patch release fixes two validator bugs: validateInternalLinks now recognises public/ assets as valid targets (no more false positives on /images/* or /fonts/*), and validateMetadataLength no longer truncates descriptions containing a raw apostrophe. Use skip only for SSR-only routes, wildcards, and [slug] params.
• Should — broken link checker in CI for external links. A lychee GitHub Action on every push to content files catches dead links before they go live; a weekly scheduled run catches link rot as external sites move or disappear. Broken outbound links are a bad UX and a negative trust signal. Internal links are covered by validateInternalLinks at build time; lychee handles everything else.
• Should — SEO strings (titles, descriptions, FAQ answers) audited for metadata quality — front-loading, concreteness, truncation fit, no title/description duplication. Phase 2.5 chains this in via metadata-check. Individual post prose can be audited separately via readability-check.

Phase 2: Improve

Based on the audit, produce the concrete code. Always ask before overwriting. Read AGENTS.md for detailed recipes.

Branch on the Phase 0 findings. If @jdevalk/astro-seo-graph is already installed, skip the install step and focus on wiring the features the audit flagged as missing (IndexNow, FuzzyRedirect, schema endpoints, build validation). If the user has a hand-rolled setup that already satisfies the Must checks in category 1, don't rip it out — add only what's missing. Replacement is a last resort, not the default.

AGENTS.md sections: Install/upgrade, Integration config, BaseHead.astro, Content collection schema, Sitemap + git lastmod, OG image route, Schema endpoints, llms.txt, Markdown alternates, API catalog, Content Signals in robots.txt, MCP and A2A discovery cards, Link headers for agent discovery, RSS feed, Redirects + FuzzyRedirect, Performance headers, Broken link checker in CI.

Phase 2.5: Metadata and readability pass

Invoke the metadata-check skill on every short string the skill generated or modified: page titles, meta descriptions, schema description fields, FAQ answers, and any blog post frontmatter excerpt values you wrote. It checks front-loading, concreteness, filler, active voice, title/description duplication, difficult words, SERP-truncation fit (title 30–65, description 70–200 — the same bounds validateMetadataLength enforces), and one-idea-per-field. Apply the fixes directly. Skip the pass entirely for technical strings (URLs, schema @id values, enum values).

If the project has a blog or docs content collection, mention to the user as a follow-up that the readability-check skill can audit individual posts for multi-paragraph prose quality — but don't audit the entire content corpus yourself.

Phase 3: Verify

• Run npm run build. If seoGraph() is wired, this also runs H1 validation, duplicate-meta detection, and schema validation — surface any warnings.
• Spot-check the built HTML: one page's <head> should now be clean, canonical correct, JSON-LD graph present and linked.
• Run the homepage through Rich Results Test and ClassySchema.
• Confirm /sitemap-index.xml exists and references per-collection sitemaps.
• If IndexNow is wired, confirm the key verification route returns the key at /[key].txt.
• Remind the user about tasks that can't be automated:
  • Register the site in Google Search Console and Bing Webmaster Tools.
  • Submit the sitemap index in both.
  • Generate an IndexNow key and commit it to config.
  • Install Plausible or equivalent privacy-friendly analytics.

Output format

## Astro SEO audit: [site name]

### Score
| Category                              | Score |
|---------------------------------------|------:|
| 1. `<Seo>` component and head         |  x/10 |
| 2. Structured data / JSON-LD graph    |  x/10 |
| 3. Content collections and schema     |  x/10 |
| 4. Open Graph images                  |  x/10 |
| 5. Sitemaps and indexing              |  x/10 |
| 6. Agent discovery                    |  x/10 |
| 7. Performance                        |  x/10 |
| 8. Redirects and error handling       |  x/10 |
| 9. Build-time validation and content  |  x/10 |
| **Total**                             | xx/90 |

### Findings
[Grouped by category. Quote actual code/config. Be specific.]

### Files generated or changed
[List with short description of each.]

### Next steps
[Non-file tasks: GSC, Bing Webmaster Tools, IndexNow key generation, analytics.]

Key principles

• Opinionated defaults over optionality. The guide picks a stack; this skill applies it. Don't offer five alternatives when one works.
• @jdevalk/astro-seo-graph is the spine. Route the <Seo> component, schema endpoints, IndexNow, FuzzyRedirect, and build validation through it unless the user has a strong reason to hand-roll.
• Topics, not keyphrases. When reviewing content, focus on topical coverage and readability, not keyword density.
• Static, CDN-served HTML is the baseline. Don't add SSR to solve problems static builds already don't have.
• Agent discovery matters now. Schema endpoints, schema map, NLWeb tags — the crawler is no longer the only consumer.