---
title: "OpenAPI: glossary: Agent Ready HTML"
description: "OpenAPI defined: A machine-readable description of an HTTP API, usually openapi.json or openapi.yaml. A dated, sourced example follows."
canonical: https://agentreadyhtml.com/glossary/openapi/
site: "Agent Ready HTML"
last_updated: 2026-11-04
section: "Glossary"
---

# OpenAPI: glossary: Agent Ready HTML

> OpenAPI defined: A machine-readable description of an HTTP API, usually openapi.json or openapi.yaml. A dated, sourced example follows.

Source: https://agentreadyhtml.com/glossary/openapi/
Site: Agent Ready HTML
Last reviewed: 2026-11-04

# OpenAPI

In short

A machine-readable description of an HTTP API, usually openapi.json or openapi.yaml. Example: On seven sites that shipped one, agents fetched openapi.json in 112 of 541 runs, or 21 percent. Related terms: Optional section, Markdown twin. Optional section: An H2 named Optional in llms.txt that holds secondary links. v2 keeps it as a convention and drops its special meaning for tools.

## Source of the example

The example in the summary above is from [vercel.com](https://vercel.com/kb/guide/make-your-site-readable-by-ai-agents), read 4 November 2026.

## Where it shows up on this site

-   [Guide: expose OpenAPI for docs](https://agentreadyhtml.com/guides/expose-openapi-for-docs/)

## Neighbouring terms

-   [Optional section](https://agentreadyhtml.com/glossary/optional-section/): An H2 named Optional in llms.txt that holds secondary links.
-   [Markdown twin](https://agentreadyhtml.com/glossary/markdown-twin/): A markdown copy of a page at a predictable URL, such as page.md or page.html.md.

## Sources

1.  [vercel.com](https://vercel.com/kb/guide/make-your-site-readable-by-ai-agents) https://vercel.com/kb/guide/make-your-site-readable-by-ai-agents, read 4 November 2026

Last reviewed 4 November 2026

Edition

Crawl

2026-11-04

Page updated

2026-11-04

Method

How the viewer reads a page, how a file is graded and how a platform is scored: [the method page](https://agentreadyhtml.com/method/).