TL;DR: HTTP 402 “Payment Required” has been reserved since 1997 but never used — because humans can’t approve per-page charges fast enough. AI agents can. The x402 protocol (Coinbase, 2025) revives 402 for stablecoin micropayments at ~$0.0001 per transaction. AWS now offers AgentCore Payments as a managed implementation. For publishers, this creates a third revenue stream beyond ads and subscriptions: validated agents pay per-article, automatically, with budget controls.

The Internet’s Most Famous Unused Feature

In 1997, the HTTP specification reserved a status code for a feature the early web assumed would arrive any day: