x402 Integrations

Production-ready x402 payment integrations for API infrastructure.

x402 is an HTTP-native payment protocol for AI agents. Instead of provisioning accounts and API keys, an agent hits an endpoint, receives a 402 Payment Required with USDC payment instructions, signs a gasless permit, and retries with the signed payment. No human in the loop.

Integrations

Integration	Stack	Status
Apify MCP middleware + E2E	TypeScript, MCP SDK, viem, USDC on Base	Reference implementation
Zuplo inbound policy	TypeScript, Cloudflare Workers	Production-ready

Apify

MCP tool-level payment middleware for call-actor with up-to scheme support. Includes exact and up-to E2E tests on Base Sepolia.

# Middleware tests (no wallet, no chain, 2 seconds)
cd apify && npm install && npx tsx test-mcp-middleware.ts

# Up-to E2E on Base Sepolia (needs funded wallet)
cd apify/e2e && npm install
PRIVATE_KEY=0x... npm run test:upto

See apify/README.md for full details.

Zuplo Policy

Drop-in inbound policy for API payment gating. 14 tests covering all edge cases.

cd zuplo && pnpm install && pnpm test

How x402 Works

Agent  ->  GET /api/resource
Server ->  402 Payment Required
           { x402Version: 2, accepts: [{ scheme, network, amount, payTo, asset, extra }] }

Agent  ->  signs ERC-2612 Permit (off-chain, free)
Agent  ->  GET /api/resource + PAYMENT-SIGNATURE header
Server ->  POST /verify to facilitator (read-only check)
Server ->  200 OK + run the job
Server ->  POST /settle to facilitator (on-chain USDC transfer)

Token Domains (EIP-712)

The ERC-2612 permit signature includes an EIP-712 domain. The name and version fields must match the on-chain token contract values:

Token	Network	name	version
USDC	Base Mainnet (eip155:8453)	USD Coin	2
USDC	Base Sepolia (eip155:84532)	USDC	2

Built by

Good Meta — x402 integrations for API infrastructure companies.