0x opens Swap API to AI agents at $0.01 per request

0x Protocol opened its Swap API to AI agents, charging $0.01 per request in USDC with no API key or account required.

The integration uses Alchemy's AgentPay middleware and the HTTP 402 Payment Required standard, a status code reserved in the original HTTP specification but never widely implemented for digital payments, according to the company's documentation.

The Swap API aggregates liquidity across more than nine chains and 130 liquidity sources covering over 9 million tokens, 0x said. The x402 network has processed 75.41 million transactions totaling $24.24 million in volume over the past 30 days, per x402.org. Payment is accepted via x402 on Base and Solana or via the Machine Payments Protocol.

The move positions 0x as infrastructure for the emerging agent-to-agent economy, where autonomous software pays for data and execution without human intermediaries. Circle released a USDC specification for MPP on June 23, adding cross-chain settlement via Circle Gateway and support for USDCx on Stacks, a Bitcoin layer-2 network.

How the payment flow works

When an AI agent sends an HTTP request to the 0x Swap API endpoint, the server returns a 402 Payment Required response. The agent then signs a USDC payment authorization on-chain using the Ethereum standard EIP-3009 and resends the request. A proxy verifies the transaction before releasing swap data. The entire process requires no API key — each request is identified by a wallet address and transaction hash.

The model removes the setup steps that have kept autonomous agents dependent on human-managed accounts. Traditional API access requires an account, a credit card, a key and a billing cycle — none of which map cleanly to a process that may execute a single swap query before spinning down.

Growing agent payment infrastructure

0x joins a stack of agent-payment infrastructure that has expanded rapidly since early June. Amazon Web Services connected Coinbase's x402 protocol to CloudFront on June 19, letting any site behind the CDN charge agents per request in USDC. Coinbase launched standalone agent accounts on June 11. Mastercard opened its card network to AI agents through the Agent Pay for Machines network with more than 30 crypto partners on June 10, and Ripple released its XRPL AI Starter Kit the same day.

0x has published dedicated documentation for AI agents, including guidance on using the Swap API programmatically and a framework called 0x Skills tailored for AI coding agents. The 0x Cross-Chain API, which entered beta in February 2026, was designed explicitly for agentic swaps.

This article is for informational purposes only and does not constitute investment advice.