What is llms.txt and Why Your Website Needs One

In 2026, a growing share of web traffic comes from AI agents — not humans clicking links, but autonomous systems browsing on behalf of users. These agents need a way to quickly understand what a website does, what APIs it offers, and how to interact with it. That's exactly what llms.txt provides.

The Problem: AI Agents Can't Read Your Website

Your website was designed for humans. It has navigation menus, hero sections, testimonials, and call-to-action buttons. An AI agent visiting your site sees HTML, CSS, JavaScript — thousands of lines of markup that bury the actual information it needs.

What the agent actually wants to know is simple: What does this website do? What services does it offer? How do I use them programmatically? What are the terms?

Without a structured way to answer these questions, agents either scrape your entire site (expensive, slow, unreliable) or skip you entirely.

What llms.txt Is

The llms.txt file is a Markdown document placed at the root of your domain (e.g., yoursite.com/llms.txt). It's designed to be consumed by large language models and AI agents. The format is simple and intentional:

• An H1 heading with your project or company name
• A blockquote with a one-line description
• Sections with links to key resources: docs, APIs, pricing, policies
• Optional: a companion llms-full.txt with complete documentation

The key insight is that Markdown is already the native language of LLMs. They're trained on it, they understand its structure, and they can parse it efficiently. No special parser needed.

A Real Example: MarketOS llms.txt

Here's a simplified version of our own llms.txt file:

# MarketOS

> AI-powered marketing content generation platform.
> Generate marketing images with captions, hashtags,
> and SEO-optimized written content.

## API Endpoints

- [Full Marketing Pipeline](/api/v1/generate/marketing):
  POST — One-shot endpoint for complete social posts.
- [Generate Caption](/api/v1/generate/caption):
  POST — Platform-specific captions and hashtags.
- [Generate Content](/api/v1/generate/content):
  POST — Blog posts, SEO articles, and 100+ types.

## Authentication

Two BYOK modes: Bearer Token (stored) or
Stateless (per-request via X-Api-Keys header).

## Pricing

BYOK model — agents pay AI providers directly.
Orchestration free during beta.

llms.txt vs robots.txt vs sitemap.xml

The Broader Agentic Discovery Ecosystem

llms.txt is part of a growing ecosystem of standards for AI agent discovery:

How to Create Your Own llms.txt

Creating an llms.txt file is straightforward. Here's a minimal template:

# Your Company Name

> One-line description of what you do.

Brief paragraph explaining your product or service.

## Key Resources

- [Documentation](https://yoursite.com/docs):
  Description of what's in the docs.
- [API Reference](https://yoursite.com/api):
  Description of your API.
- [Pricing](https://yoursite.com/pricing):
  How your pricing works.

## Policies

- [Terms](https://yoursite.com/terms)
- [Privacy](https://yoursite.com/privacy)

Place this file at your domain root so it's accessible at yoursite.com/llms.txt. Set the Content-Type header to text/markdown; charset=utf-8 and add Access-Control-Allow-Origin: * so agents from any origin can read it.

Why This Matters for SEO

AI-powered search engines like Perplexity, ChatGPT Search, and Google's AI Overviews are increasingly citing sources. If your website is easily parseable by AI systems, you're more likely to be referenced in AI-generated answers. An llms.txt file makes your site's purpose and content immediately clear to these systems.

Think of it as SEO for the AI era: instead of optimizing for keyword crawlers, you're optimizing for language models that need to understand what you do in order to recommend you.

Check out our llms.txt for a production example, or read about how we built the MarketOS Agentic API that it describes.