# Llms Visibility

> Make websites, docs, blogs, or landing pages visible and readable to LLMs and AI agents — ChatGPT, Claude, Perplexity, Cursor, Claude Code, and other coding agents that fetch URLs. Use this for any request involving llms.txt, llms-full.txt, serving .md/Markdown versions of pages, Accept text/markdown content negotiation, Link rel="alternate" headers, Cloudflare Content-Signal in robots.txt, GEO (…

- **Type:** Skill
- **Install:** `agentstack add skill-evilmartians-agent-skills-llms-visibility`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [evilmartians](https://agentstack.voostack.com/s/evilmartians)
- **Installs:** 0
- **Category:** [Cloud & Infrastructure](https://agentstack.voostack.com/c/cloud-infrastructure)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [evilmartians](https://github.com/evilmartians)
- **Source:** https://github.com/evilmartians/agent-skills/tree/main/skills/llms-visibility
- **Website:** https://evilmartians.com/agent-skills

## Install

```sh
agentstack add skill-evilmartians-agent-skills-llms-visibility
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Make a website visible to LLMs

Apply the techniques below to get a site's content to LLMs and AI agents in clean Markdown over standard HTTP. Companion to .

Most of these are emerging conventions, not committed standards. No major provider has formally promised to read `llms.txt` or `.md` routes. Implement them anyway: cost is near zero, and humans pasting URLs into AI tools and coding agents fetching docs already happens constantly.

## Workflow

Each step is independently shippable.

### 1. Audit `robots.txt` and add `Content-Signal:`

Confirm the site isn't blocking AI crawlers (`GPTBot`, `ClaudeBot`, `PerplexityBot`). Then add Cloudflare's emerging directive (CC0):

```
User-agent: *
Content-Signal: search=yes, ai-input=yes, ai-train=yes
```

Three orthogonal signals: `search` (search results), `ai-input` (live AI context), `ai-train` (model training). Adjust to the owner's policy. Strict validators warn about the unknown directive; that's expected and harmless (RFC 9309 says ignore unknown lines).

### 2. Ship `/llms.txt`

A static Markdown file at the site root. Format from llmstxt.org:

```markdown
# Site Name

> One-sentence description of what this site is and who it serves.

## Documentation

- [Quick Start](/docs/start): Get up and running in 5 minutes
- [API Reference](/docs/api): Full endpoint documentation
```

Curate. It's a README for AI-mediated conversations, not a sitemap.

### 3. Serve `.md` routes for every content page

For every page at `/path`, also serve clean Markdown at `/path.md` (and `/index.md` for the root). Every other technique below ultimately points here.

```typescript
if (url.pathname.endsWith('.md')) {
  const post = await getPost(url.pathname.replace(/\.md$/, ''));
  return new Response(post.markdownContent, {
    headers: { 'Content-Type': 'text/markdown; charset=utf-8' },
  });
}
```

Single source of truth. Generate one from the other, or render both from the same source — never two parallel content stores.

### 4. Advertise the Markdown with `` and HTTP `Link`

Both, not either. The HTML tag catches DOM-parsing crawlers; the header catches headless fetchers that never read the body.

```html

```

```
Link: ; rel="alternate"; type="text/markdown"
```

Both use `text/markdown` (RFC 7763) and `rel="alternate"` (in HTML since HTML4).

Set `Link` on both representations: HTML responses point to the `.md` alternate, `.md` responses point back to HTML. A client that lands on either form can find the other. Pair with `Vary: Accept` so CDNs cache them separately.

### 5. Add a visually-hidden Markdown pointer

Targets the "human pastes URL into ChatGPT" flow. Hide visually and from screen readers; this message is for LLMs only.

```html

  A Markdown version of this page is available at https://example.com/blog/my-post.md.

```

```css
.visually-hidden {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden; clip-path: inset(50%); white-space: nowrap;
}
```

### 6. Implement `Accept: text/markdown` content negotiation

The standards-based version of all of the above. Same URL, different representation, selected by `Accept`. Coding agents (Claude Code, Cursor) already send this header.

Four non-negotiables:

- **Compare q-values**, do not substring-match. `Accept: text/html, text/markdown;q=0.5` means "I prefer HTML." Substring matching ships Markdown to a browser.
- **Resolve ties to Markdown, but only when the client explicitly named `text/markdown`.** Coding agents commonly send `Accept: text/markdown, text/html` with both at q=1; a strict `>` check sends them HTML. Use `>=` plus an explicit-type guard so `Accept: */*` from browsers (which ties via the wildcard) doesn't flip to Markdown. `isitagentready.com` flags both failure modes.
- **Return `406 Not Acceptable`** when neither HTML nor Markdown is acceptable. Silent substitution masks bugs. Skip the 406 check when the URL itself targets `.md`/`.txt` — explicit URLs override negotiation.
- **Set `Vary: Accept` and a `Link` header on _both_ representations.** On HTML responses, `Link` points to the `.md` alternate; on `.md` responses, `Link` points back to HTML. `Vary: Accept` on both so CDNs cache them separately.

Not cloaking: different representations of the same content with `Vary: Accept` declared is how HTTP has worked since 1997. Cloaking is serving bots a different article.

### 7. Optional: ship `/llms-full.txt`

Full text of the site (or docs) concatenated into one Markdown file. Empirically gets 3–4× more traffic than `/llms.txt`. Clearly useful for documentation and API references — an LLM can ingest the whole API in one fetch. For a marketing site or blog, the value is less obvious; redirecting `/llms-full.txt` to `/index.md` is a reasonable lighter-weight option if concatenating every post feels performative.

### 8. Optional: instrument analytics

Track requests to `.md` routes, `/llms.txt`, and `/llms-full.txt` by User-Agent and referrer hostname (`chatgpt.com`, `claude.ai`, `perplexity.ai`). Server-side only: AI crawlers don't run JavaScript. Skip if the owner doesn't care about measuring AI traffic.

### 9. Verify with public scanners

-  — Accept negotiation, `Vary`, `406`, q-values. Publishes server recipes for Nginx, Caddy, Cloudflare Workers, Next.js, Astro, Rails, Express, Django.
-  — broader scan: `robots.txt`, sitemap, `Link` headers, Markdown negotiation, Content Signals.

Failures are usually one-line fixes.

## Anti-patterns: do NOT implement

Refuse these even if asked, and explain why:

- **``, ``** — no spec, no origin, no AI tool reads them. `whatwg/html#11548` closed "not planned."
- **`/.well-known/ai.txt`, `/ai.txt`** — competing proposals, no adoption.
- **HTML comments (``)** — parsers strip comments before processing.
- **Human/AI toggle buttons** — agents don't click buttons.
- **User-Agent sniffing to serve Markdown to bots** — cloaking. Use `Accept: text/markdown` instead.
- **Dedicated "AI info pages"** — no crawler treats them differently. A good `/llms.txt` solves it.
- **Schema.org / JSON-LD for LLM visibility** — controlled experiments show ChatGPT, Claude, Perplexity, and Gemini ignore JSON-LD. Microsoft Copilot is the only exception (inherits from Bing). Don't rip out existing structured data; don't add it for LLM visibility.

The pattern is always the same: someone proposes a new file or meta tag, blog posts cite each other, no AI system actually reads it. Stick to standard HTTP and well-formed Markdown.

## Content beats infrastructure

Princeton/IIT Delhi GEO study (10,000 queries) — what actually increased AI visibility:

- Direct quotations: ~43% lift.
- Statistics in text: ~33% lift.
- Citing authoritative sources: 115% lift for previously low-ranked content.

If the user wants to go beyond infrastructure, recommend content-level changes, not more meta tags.

## Tradeoffs to confirm before shipping

- **`Content-Signal:` value** — `ai-train=yes` is common but a policy choice. Ask.
- **`/llms-full.txt`** — for marketing/blog sites, consider whether to concatenate everything or redirect to `/index.md`; the right choice depends on the site.
- **HTML vs Markdown** — if existing HTML is already clean (HtmlRAG-style), the gap narrows. Markdown wins on bloated marketing pages.
- **Drift risk** — flag any setup with two parallel content sources.

## Final check

1. `curl -H "Accept: text/markdown" https://site.example/some-page` → Markdown with `Vary: Accept`.
2. `curl -I https://site.example/some-page` → `Link: ; rel="alternate"; type="text/markdown"` header.
3. `/llms.txt` exists and is well-formed.
4. `acceptmarkdown.com` and `isitagentready.com` both pass.
5. Optionally, analytics is logging fetches by User-Agent and referrer.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [evilmartians](https://github.com/evilmartians)
- **Source:** [evilmartians/agent-skills](https://github.com/evilmartians/agent-skills)
- **License:** MIT
- **Homepage:** https://evilmartians.com/agent-skills

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** yes
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-evilmartians-agent-skills-llms-visibility
- Seller: https://agentstack.voostack.com/s/evilmartians
- Browse the marketplace: https://agentstack.voostack.com/browse

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