Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add BestLemoon/codex-seo --skill seo-hreflanggit clone --depth 1 https://github.com/BestLemoon/codex-seoWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/bestlemoon/codex-seo/seo-hreflang)<a href="https://agentmods.dev/skills/bestlemoon/codex-seo/seo-hreflang"><img src="https://agentmods.dev/badge/skills/bestlemoon/codex-seo/seo-hreflang/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/bestlemoon/codex-seo/seo-hreflang"><img src="https://agentmods.dev/badge/skills/bestlemoon/codex-seo/seo-hreflang.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00071 | $0.02233 |
| Opus 5.5 | $0.00028 | $0.00893 |
| Sonnet 5.5 | $0.00014 | $0.00447 |
| Haiku 4.5 | $0.00007 | $0.00223 |
Grade A, and why
seo-hreflang scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
88% identical to seo-hreflang — 115 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 200 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Hreflang & International SEO
Validate existing hreflang implementations or generate correct hreflang tags for multi-language and multi-region sites. Supports HTML, HTTP header, and XML sitemap implementations.
Validation Checks
1. Self-Referencing Tags
- Every page must include an hreflang tag pointing to itself
- The self-referencing URL must exactly match the page's canonical URL
- Missing self-referencing tags cause Google to ignore the entire hreflang set
2. Return Tags
- If page A links to page B with hreflang, page B must link back to page A
- Every hreflang relationship must be bidirectional (A→B and B→A)
- Missing return tags invalidate the hreflang signal for both pages
- Check all language versions reference each other (full mesh)
3. x-default Tag
- Required: designates the fallback page for unmatched languages/regions
- Typically points to the language selector page or English version
- Only one x-default per set of alternates
- Must also have return tags from all other language versions
4. Language Code Validation
- Must use ISO 639-1 two-letter codes (e.g.,
en,fr,de,ja) - Common errors:
enginstead ofen(ISO 639-2, not valid for hreflang)jpinstead ofja(incorrect code for Japanese)zhwithout region qualifier (ambiguous; usezh-Hansorzh-Hant)
5. Region Code Validation
- Optional region qualifier uses ISO 3166-1 Alpha-2 (e.g.,
en-US,en-GB,pt-BR) - Format:
language-REGION(lowercase language, uppercase region) - Common errors:
en-ukinstead ofen-GB(UK is not a valid ISO 3166-1 code)es-LA(Latin America is not a country; use specific countries)- Region without language prefix
6. Canonical URL Alignment
- Hreflang tags must only appear on canonical URLs
- If a page has
rel=canonicalpointing elsewhere, hreflang on that page is ignored - The canonical URL and hreflang URL must match exactly (including trailing slashes)
- Non-canonical pages should not be in any hreflang set
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 200 lines · 71 tokens per session scan A eab248b9c506
seo-hreflang is a skill published in the GitHub repository BestLemoon/codex-seo (9 stars, last pushed 3mo ago), licensed MIT. It adds 71 tokens to every session and 2,233 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 88% identical to seo-hreflang, differing in 115 lines, and is treated as a copy.
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