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 lionkiii/claude-seo-skills --skill seo-llms-txtgit clone --depth 1 https://github.com/lionkiii/claude-seo-skillsWrote 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/lionkiii/claude-seo-skills/seo-llms-txt)<a href="https://agentmods.dev/skills/lionkiii/claude-seo-skills/seo-llms-txt"><img src="https://agentmods.dev/badge/skills/lionkiii/claude-seo-skills/seo-llms-txt/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/lionkiii/claude-seo-skills/seo-llms-txt"><img src="https://agentmods.dev/badge/skills/lionkiii/claude-seo-skills/seo-llms-txt.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 | $0.00072 | $0.02167 |
| Opus 5 | $0.00036 | $0.01084 |
| Sonnet 5 | $0.00014 | $0.00433 |
| Haiku 4.5 | $0.00007 | $0.00217 |
Grade A, and why
seo-llms-txt 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 12d 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.
How it starts
The opening of the file, as written. The whole thing — 235 lines — stays where its author put it; the contents beside it link to each section on GitHub.
llms.txt — Generate, Validate & Audit
Analyze, generate, or validate llms.txt files per the llms.txt specification
(proposed by Jeremy Howard / Answer.AI). The llms.txt standard provides a
Markdown file at /llms.txt that helps LLMs understand a website's content
structure — similar to how robots.txt guides traditional crawlers.
Adoption: Adopted by thousands of sites including Anthropic, Cloudflare, Docker, Vercel, Stripe, FastHTML, Cursor, Hugging Face, and many more.
Lighthouse "Agentic Browsing" audit
Chrome Lighthouse now includes an Agentic Browsing audit category with a
dedicated llms.txt check. Lighthouse flags a page if a server error occurs
when fetching /llms.txt; if the file is simply absent (404), the audit is
marked Not Applicable since the file is optional. Users can validate their
llms.txt presence by running Lighthouse. Reference:
https://developer.chrome.com/docs/lighthouse/agentic-browsing/llms-txt
Inputs
Three modes, auto-detected from the user's input:
| Input Pattern | Mode | Example |
|---|---|---|
/seo llms-txt <url> |
Audit | /seo llms-txt example.com |
/seo llms-txt generate <url> |
Generate | /seo llms-txt generate example.com |
/seo llms-txt validate <url-or-path> |
Validate | /seo llms-txt validate /path/to/llms.txt |
- If user provides a URL without sub-command → Audit mode (fetch and check existing file)
- If user says "generate" → Generate mode (crawl site, produce llms.txt)
- If user says "validate" → Validate mode (parse and check against spec)
llms.txt Spec Reference
@skills/seo/references/llms-txt-spec.md
Quick Spec Summary
The llms.txt file must be valid Markdown with this structure:
- H1 heading (required) — Project/site name
- Blockquote (optional) — Short site summary
- H2 sections — Categorized link lists with descriptions
- Link format:
- [Name](url): Description(colon + space after URL) ## Optionalsection — Links useful but not essential for understanding- Companion files (optional):
llms-full.txt— Comprehensive version with full content- Individual
.mdpage mirrors for key pages
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.
- 12d ago First seen · 235 lines · 72 tokens per session scan A ff1305ec446b
seo-llms-txt is a skill published in the GitHub repository lionkiii/claude-seo-skills (20 stars, last pushed 3mo ago), licensed MIT. It adds 72 tokens to every session and 2,167 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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