x402

Production

HTTP 402 Payment Required — Coinbase

Overview

x402 is Coinbase's open protocol for machine-to-machine payments using the HTTP 402 status code. When an AI agent hits a paid endpoint, it receives a 402 response with on-chain payment instructions. The agent pays with USDC, and the server verifies the payment before serving the response. SettleGrid runs a public x402 facilitator (verify + settle on Base) as a standalone service; the metering, budgets, and analytics layer SettleGrid adds on top — and settling x402 through the hosted proxy for your own tool's revenue — is in development.

How It Works

The x402 flow begins when an AI agent sends a request to a paid endpoint without a payment header. The server responds with HTTP 402 and a JSON body specifying the price, the accepted token (USDC), network, and a payment address. The agent constructs an on-chain transaction, signs it, and resends the request with the payment proof in a custom header.

The server verifies the on-chain payment (checking amount, recipient, and confirmation status) before processing the request. This creates a trustless, permissionless payment channel between any two machines on the internet.

On top of that on-chain flow, SettleGrid is building a platform layer that adds credit-based budgets, rate limiting, and analytics. When that layer is live, instead of raw on-chain verification on every call, consumers will be able to pre-fund a credit balance with USDC and let SettleGrid handle the metering — reducing gas costs and latency while keeping the crypto-native payment model. That metering, budgets, and analytics layer — settling x402 through SettleGrid's hosted proxy for your own tool's revenue — is in development; the standalone facilitator that verifies and settles x402 on Base is live today.

How SettleGrid Integrates

SettleGrid runs a live standalone x402 facilitator: three API endpoints handle the flow — /api/x402/verify and /api/x402/settle verify and settle USDC payments on Base, and /api/x402/supported lists the accepted networks. Settling x402 through SettleGrid's hosted proxy on your tool's behalf — crediting your developer balance and metering each invocation — is in development. When that platform layer is live, a consumer's agent sends an x402 payment header, SettleGrid verifies the transaction, credits the developer's balance, and meters the invocation; developers receive payouts in fiat via Stripe Connect regardless of how the consumer paid.

Key Specs

Protocol	x402 — HTTP 402 Payment Required
Backer	Coinbase
Detection Header	X-402-Payment / X-Payment-*
Identity Type	wallet-address
Payment Type	on-chain USDC (Base)
Status	Production

Code Example

Here is how a developer's tool works with x402 via SettleGrid:

x402-example.tstypescript

import { settlegrid } from '@settlegrid/mcp'

const sg = settlegrid.init({
  toolSlug: 'blockchain-analytics',
  pricing: { defaultCostCents: 25 },
  // x402 payments are verified automatically
  // Consumer agents pay with USDC on-chain
})

const analyze = sg.wrap(async (args: { address: string }) => {
  const analysis = await analyzeWallet(args.address)
  return { content: [{ type: 'text', text: JSON.stringify(analysis) }] }
}, { method: 'analyze-wallet' })

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