x402 协议：用 HTTP 402 让智能体自动付费
介绍 Coinbase 的 x402 协议，把闲置的 HTTP 402 变成付费请求流程：服务器报价、智能体用 USDC 付款即通过，无需账号或 API key，Vangrid 是早期应用。
The most important HTTP status code you have never used: 402. It means "Payment Required." Reserved since 1999, it sat empty for 25 years because the web never had native payments. Then crypto showed up. Coinbase's x402 turns it into a working protocol: a server answers 402 with a price, the agent pays in USDC, the request goes through. No account, no API key, no signup form. @vangrid_io is one of the earliest real applications: - An agent POSTs to /bounties and gets back a 402 quoting the bounty price in USDC - It pays on Base or Arc, and the bounty is live on the board within about a minute - Nothing worth accepting? Cancel or let it expire, and the full amount is refunded on-chain One agent-commissioned bounty exists on-chain so far. The plumbing is real; the traffic is not there yet. Watch this primitive. The agent economy needs a cash register, and 402 might be it.