x402 · agentic payments · open web

Payment rails
for agents.

rail is HTTP-native pay for AI agents — built on x402. Your agent hits a paid API, settles in stablecoins, and keeps going. No accounts. No API keys. No human in the loop.

See the flow Drop in middleware

402 payment required

$0 protocol fees

~ms settle & retry

0 API keys

rail agents pay · x402

How it works

Request → 402 → pay → continue

Same HTTP your stack already speaks. x402 made status code 402 useful again — rail is how agents ride it.

Agent calls an API

No signup, no credit card form. Just a normal request to a paid endpoint.

Server returns 402

Machine-readable payment terms: amount, token, network, pay-to. Stateless. No session.

Agent pays & retries

Signs a stablecoin transfer, resubmits with proof. Facilitator settles. Content unlocks.

GET /costly-data

→

402 Payment Required

→

sign USDC

→

200 + payload

Works with Solana SPL tokens, EVM stablecoins, and any chain the server accepts. Facilitator handles onchain submit so APIs don’t need a full wallet stack.

Why agents need this

The old way breaks flow state

Before

Create account at every API
KYC + card on file
Buy credits / subscriptions
Store & rotate API keys
Human babysits every vendor

With rail / x402

One wallet, many services
Pay-per-request micropayments
No API keys to leak
Zero protocol fees
Agent runs unattended

Build

One line of middleware

Charge per request. Accept any network the x402 stack supports.

server.ts

// require payment for paid routes
app.use(
  paymentMiddleware({
    "GET /costly-data": {
      accepts: [{
        scheme: "exact",
        price: "$0.001",
        network: "solana:…",
        payTo: svmAddress,
      }],
      description: "Costly data",
      mimeType: "application/json",
    },
  })
);

◎

Sell to agents

Monetize APIs, data, and compute with pay-per-use — no sales funnel for machines.

⚡

Buy as an agent

Fund a wallet, set a spend ceiling, let the agent settle 402s mid-task.

🔗

Chain-agnostic

Solana, Base, and more. Stablecoins first. Open standard under the Linux Foundation.

🛡

No keys, no sessions

Stateless HTTP. Payment proof rides with the request. Nothing sticky to rotate.

Stack

Tools on the rail

x402 Open payment protocol · HTTP 402 Solana agentic pay Docs · pay CLI · facilitators x402 docs Seller & buyer quickstarts pay.sh CLI that wraps curl / agents

Put your API on the rail

Price an endpoint. Let agents settle in-band. That’s the whole product.

Seller quickstart Buyer quickstart

Payment rails for agents.