Which AI agents support Markdown content negotiation?

Verify an AI agent yourself

We test the matrix ourselves, but AI agent behavior shifts across versions, plans, and newly-added tools. You can corroborate any row — or catch a regression — by triggering an agent against your own server and reading the request from your access logs.

1. Capture the Accept header in your logs

Default log formats usually drop it. Add it once:

log_format with_accept '$remote_addr - $remote_user [$time_local] '
                       '"$request" $status $body_bytes_sent '
                       '"$http_referer" "$http_user_agent" '
                       'accept="$http_accept"';
access_log /var/log/nginx/access.log with_accept;

2. Trigger a known AI agent against a specific URL

Pick a URL on your site — ideally a unique or freshly-published one so the request isn't masked by background traffic. Then ask the agent to fetch or summarize it:

• ChatGPT — "Summarize https://yoursite.com/article-xyz" (with the browse tool enabled)
• Claude — "What does https://yoursite.com/article-xyz say?" (requires web_fetch / web_search)
• Perplexity — paste the URL directly into a query
• …and so on for whichever agent you're testing.

3. Report what you saw

Grep for the URL in your access log and send the line(s) to feedback, along with the agent you used and the prompt you sent. The accept= field tells us whether text/markdown was advertised.