---
title: "Vary: Accept defined | Agent Ready Checklist"
description: "Vary: Accept: Response header telling caches the body depends on the Accept request header, so HTML and markdown variants are stored apart."
canonical: https://agentreadychecklist.com/glossary/vary-accept
site: "Agent Ready Checklist"
last_updated: 2026-11-05
section: "Glossary"
---

# Vary: Accept defined | Agent Ready Checklist

> Vary: Accept: Response header telling caches the body depends on the Accept request header, so HTML and markdown variants are stored apart.

Source: https://agentreadychecklist.com/glossary/vary-accept
Site: Agent Ready Checklist
Last reviewed: 2026-11-05
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# Vary: Accept

Response header telling caches the body depends on the Accept request header, so HTML and markdown variants are stored apart. Example: Content-Type: text/markdown; charset=utf-8 Vary: Accept. Related row: VERCEL-NEGOTIATION-HEADERS (Markdown headers). The Vercel guide adds the Content-Type and Vary: Accept rule; the AgentReady spec text has no equivalent line. The row "Markdown headers" names Vary: Accept.

## Definition

Response header telling caches the body depends on the Accept request header, so HTML and markdown variants are stored apart.

## Example

```text
Content-Type: text/markdown; charset=utf-8
Vary: Accept
```

## Where it appears on the checklist

-   [VERCEL-NEGOTIATION-HEADERS](https://agentreadychecklist.com/checklist/vercel-negotiation-headers/)Markdown headers: If you serve markdown by negotiation, answer Accept: text/markdown with Content-Type: text/markdown; charset=utf-8 and Vary: Accept; when markdown is unavailable, return HTML with its correct content type.

## Asked about it

### Is markdown content negotiation required?

Not by AgentReady. AR-READ-09 (MAY) is about advertising a mirror, and the spec says negotiation did not change success in the studies. Cloudflare scores negotiation as a check. If you do it, send Content-Type text/markdown and Vary: Accept.

## Sources

-   [vercel.com/kb/guide/make-your-site-readable-by-ai-agents](https://vercel.com/kb/guide/make-your-site-readable-by-ai-agents)read 2026-11-04
-   [github.com/agentready-org/standard/blob/main/spec/spec.md](https://github.com/agentready-org/standard/blob/main/spec/spec.md)read 2026-11-04

Last reviewed 2026-11-05. AgentReady v2.0, read 2026-11-04.