# x402 Payments Are Live: The Stablecoin Rail Crypto APIs launches a managed x402 facilitator — add a stablecoin paywall to any API and let your AI agents pay 402-gated endpoints, fully non-custodial. *Published 2026-07-28* ## The payment problem nobody built for machines Every payment system we use was designed for a human: a person typing a card number, clicking "subscribe," approving a checkout. That model breaks the moment the buyer is software. An AI agent can't open an account, pass a KYC form, or click a confirmation button — but it increasingly needs to buy things: an API call, a dataset, a compute cycle, a tool invocation. For nearly 30 years the HTTP spec has held a reserved status code for exactly this moment: 402 Payment Required. Reserved in the late ‘90s, it was never standardized — a placeholder waiting for a payment system that didn’t exist yet. That system now exists. It's called x402, and today Crypto APIs is launching a managed facilitator for it. ## [What x402 actually does](https://www.youtube.com/playlist?list=PLRozQuY3RSJs) x402 is an open protocol for paying for HTTP APIs with stablecoin, using the standard 402 response. The flow is simple enough to describe in one sentence: An agent requests a paid endpoint → the server replies with 402 Payment Required and the price → the agent signs a USDC payment locally → it retries the request with the signed payload attached → the server verifies and settles onchain, then returns the data. The entire cycle takes seconds, requires no login, and settles onchain with zero protocol fees. It's already moved serious volume — over 119 million transactions on Base and roughly $600M in annualized volume across the ecosystem — and it's growing precisely because the agent economy needs a rail built for machines. ## Why both sides matter Here's the part that's rarely discussed: x402 only works if both halves of the transaction are solved. You need the seller side — an API that can issue a 402 challenge, verify a signed payment, and settle it — and the buyer side — an agent that can read the challenge, sign, and retry. Building either from scratch means running gas wallets, verifying EIP-712 signatures, broadcasting settlements, enforcing spending limits, and staying non-custodial through all of it. Crypto APIs handles both. ## Monetize any API (the seller side) Add a per-request paywall to your endpoint in a few lines. Our zero-dependency, non-custodial merchant SDK (@cryptoapis-io/x402-merchant-sdk) ships as drop-in middleware for Express, Hono and Next.js. Under the hood it calls a managed facilitator: - POST /verify — validate a buyer's signed payment without settling - POST /settle — verify, then broadcast the settlement onchain using our gas wallet - GET /supported — list live assets, networks and signers Every response carries settlement-quota headers (X-X402-Settlement-Limit, -Remaining, -Reset) so you can watch your billing cycle and self-throttle before you hit a limit. ## Let your agents pay (the buyer side) On the other side, your apps and agents can pay 402-gated endpoints automatically using our buyer SDK, an x402_pay MCP tool, and an agent plugin. Payments are signed locally with EIP-712 — your keys never leave your side, and there is no /sign endpoint. You keep full custody. And because runaway spend is the first thing anyone worries about with autonomous payments, we enforce per-transaction, daily and monthly spending limits out of the box. ## Non-custodial, by design This is the point we won't compromise on. The facilitator verifies signatures and settles on-chain, but it can never move funds beyond what the buyer explicitly authorized. The client signs every payment locally. Settlement happens in USDC across supported EVM networks like Base. ## Get started x402 is live now on Crypto APIs, available on every paid plan — starting with Starter at $49/month, or $40/month billed annually. Scale up through Scale, Pro and Enterprise as your volume grows. - 🔗 [Product overview](https://cryptoapis.io/products/x402) - 📖 [Merchant & Facilitator API docs](https://developers.cryptoapis.io/v-2.2024-12-12-175/RESTapis/x402/x402-merchant-facilitator) - 💳 [Pricing](https://cryptoapis.io/pricing) The agent economy is being built right now. x402 is how it pays. Let's build it together. --- More on the [Crypto APIs blog](https://cryptoapis.io/blog), or see the [products](https://cryptoapis.io/products) this is built on.