{"rule_id":"AB-019","category":"content_negotiation","icon":"🎯","title":"Preferred Format Selection","short_description":"Your site respects format preferences when agents specify what they want.","user_value":"When an agent says 'I prefer JSON over HTML', your site should honor that preference.","wrong_example":"Format preferences are ignored. Agents get whatever the server decides.","right_example":"Format preferences are respected, so agents get exactly what they asked for.","effort_hint":"moderate","estimated_cost":"$10-50","severity":"low","pillar":"discovery","version":"1.0.0","counted_in_score":true,"check":{"type":"header_check","sources":["content_negotiation"],"target":"/"},"fix":{"eligible":false,"type":"assisted","note":"Implement q-value based content negotiation per RFC 7231"},"checklist_anchor":"#AB-019","checklist_url":"/agent-readiness-checklist#AB-019","html_url":"/rules/AB-019","json_url":"/rules/AB-019.json","related_rules":[{"rule_id":"AB-015","title":"Agent User-Agent Format","category":"content_negotiation"},{"rule_id":"AB-016","title":"JSON Format Support","category":"content_negotiation"},{"rule_id":"AB-017","title":"Plain Text Format Support","category":"content_negotiation"},{"rule_id":"AB-018","title":"Markdown Format Support","category":"content_negotiation"},{"rule_id":"AB-028","title":"Vary Header","category":"content_negotiation"},{"rule_id":"AB-029","title":"No Redirect on Negotiation","category":"content_negotiation"}]}