The Rate Limit Announcement

We are introducing or tightening rate limits: [CURRENT USAGE DISTRIBUTION, WHO GETS HURT - TOP TEN BY VOLUME, THE NEW LIMITS AND TIERS, THE WHY IN ONE HONEST SENTENCE]. Write the announcement: the limits table developers can plan against, who is affected and exactly how (usage percentile, not 'a small number of users'), the grace period and the headers or errors they will see, the path to a higher tier with a real contact, and the internal playbook for the angry tweets and tickets in week one.