Every team builds APIs. Few build ones that survive their second rewrite. After inheriting three different REST APIs in as many years — one with endpoints named /getAllUsers , another that returned { "status": "ok" } for both success and 500 errors — I started keeping a list of the practices that actually distinguish robust APIs from ones that generate PagerDuty alerts at 3 AM. This guide distills six rules I've validated across production services handling tens of millions of requests. ...