Fix: AI user-fetch User-Agent receives the markdown twin

Web-audit fix skill for the markdown-agent-ua check (Content for agents, MAY).

Goal

Serve the markdown twin to AI on-demand user-fetchers that state no content-type preference.

Fix

Recognize the AI on-demand user-fetch User-Agents (ChatGPT-User, Claude-User, Perplexity-User) and serve them the markdown twin when they send Accept: */* or no Accept. These fetchers retrieve a page on a person's behalf and parse markdown far more reliably than a JS-rendered page, so handing them source improves what the assistant reads back. Match the token case-insensitively and fall through to HTML for everything you do not recognize.

Resources

• RFC 7763 (text/markdown)
• OpenAI bots and User-Agents

Copy-paste prompt

Paste this into your coding agent. Your audit adds what it observed for this check:

Verify

Re-run the audit at https://anc.dev/audit or call the audit_website MCP tool; the markdown-agent-ua check should report pass.