// GLOSSARY -- X402
What is a Pay-Per-Use API?
A pay-per-use API charges per request using crypto micropayments rather than flat subscriptions. With x402, AI agents pay per call using stablecoins in real-time.
WHY IT MATTERS
Subscriptions don't fit agents — 10,000 API calls one day, zero the next. Pay-per-use aligns costs with consumption.
Stablecoin L2 transfers cost fractions of a cent, making $0.001-per-call viable. x402 standardizes this: server responds 402, agent pays, resource delivered.
New business model for providers — monetize every request without subscriptions. Agents get fine-grained access to any implementing service.
HOW POLICYLAYER USES THIS
PolicyLayer prevents runaway API costs — per-API budgets, daily caps, and velocity limits keep thousands-of-calls-per-minute scenarios predictable.
FREQUENTLY ASKED QUESTIONS
How cheap?
L2 tx fees under $0.01, making fractions-of-a-cent charges viable with stablecoin micropayments.
Which APIs support this?
Emerging ecosystem — some AI inference, data, and compute services support x402. Rapid growth as the standard gains adoption.
How does pricing work?
Server specifies price in the 402 response. Agent accepts/pays or rejects and tries another provider.