x402: How AI Agents Pay for API Calls with HTTP

Every second, AI agents hit rate limits, quota caps, and "payment required" errors that kill their workflows. They can reason about complex problems but can't pay a $0.02 API fee. Meanwhile, human developers juggle credit cards, subscription billing, and manual account management just to keep their agents running. The bottleneck isn't intelligence - it's payments. AI agents need economic agency to participate in the digital economy, and that requires wallet infrastructure designed for autonomous operation, not human oversight.