x402 payments

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An AI agent pays an online store with x402 when the store answers a request with HTTP 402 Payment Required and the agent retries with a signed payment. The agent pays in USDC stablecoin, and the store checks that payment before it returns the goods or data. The Integrator charges 0% fee during the pilot.

How an agent pays a store with x402

x402 reuses the HTTP request cycle that web stores already run. The agent asks for a paid resource. The store does not return the resource yet. It answers with status 402 and a description of the payment it accepts.

That description names the price, the currency and the payment network. The agent reads the terms and builds a payment that matches them. It then sends the same request again with the payment attached. The store checks the payment and returns the resource.

• The agent requests a paid resource.
• The store answers with status 402 and the payment terms.
• The agent signs a payment that matches the terms.
• The agent retries the request with the payment attached.
• The store verifies the payment and returns the resource.

The loop does not require a checkout page. The agent signs the payment with the wallet it controls, so no human types card details into a form.

Why HTTP 402 matters for store owners

HTTP defines status code 402 as Payment Required. RFC 9110 lists it as reserved for future use. The status code does not say how payment works. x402 fills that gap with a defined payment description and a defined retry, so a store and an agent can agree on terms without a shared account. The specification is at RFC 9110, section 15.5.3.

A store that already serves HTTP can add the 402 response to routes that cost money. Routes that stay free keep their normal response. The store does not need a second site for agents, because the same routes serve both buyers and agents.

What the store must decide before it opens paid routes

The store owner makes three decisions before the first agent payment arrives.

• The price for each paid route, in USDC stablecoin.
• The routes that stay free.
• The payment network named in the terms.

Set each price to match the price shown to human buyers. An agent compares the terms with its budget. If the price is higher than the budget, the agent stops and does not pay.

Free routes help an agent test the store before it pays. A free route answers without a 402 response, so the agent can confirm that the data matches what it needs.

What the agent checks before it pays

A careful agent reads the 402 response before it signs anything. It checks four fields.

• The price in the payment terms.
• The currency, which must be USDC stablecoin.
• The payment network named in the terms.
• The route it requested, so the payment matches that resource.

An agent that skips these checks can pay more than it planned or pay for the wrong resource. The checks cost the agent a few reads of the response, so there is no reason to skip them.

Where the Integrator fits

The Integrator connects an online store to agent payments. The Integrator charges 0% fee during the pilot. Read that fee before you connect a store, and compare it with the cost of building the same payment flow yourself.

The Integrator sets a minimum order of $1.00. Purchases below that amount need a free route or another price model. A store with many small items can price bundles instead of single units, so each agent purchase clears the minimum.

In this setup, payments settle on Base and Tempo. The store confirms settlement before it delivers paid goods. Delivery before settlement lets an unpaid order through, so the order of those two steps matters.

Caveats to plan for

Prices can change between the 402 response and the retry. The store should quote a price that stays valid for a short window. A changed price should fail the retry, and the agent should ask again for fresh terms.

• Agent wallets hold real funds. Limit the balance each agent carries.
• A payment for one route must not grant access to another route. Check the requested route on each request.
• Mistakes happen on both sides. Keep order records that show the price, the route and the settlement.

Agent payments are new to most shoppers. Explain the price on the product page in plain words, so a human can check what an agent will pay for the same item.

A first test, step by step

Start with one route and one low-cost resource. Run the full loop before you open more routes.

• Price one route in USDC stablecoin and leave the rest free.
• Send a test payment from an agent wallet with a small balance.
• Confirm that the store delivers the resource only after settlement.

If the test passes, open the next route and repeat the same checks. If it fails, fix the price or the payment check before you open any more routes.

Fees and limits

• Cost to the store: 0% fee during the pilot.
• Minimum order: $1.00.
• Rails: Base and Tempo.

FAQ

Recommended next step

1. STEP 1/2 Connect AI payment to your store
2. STEP 2/2 Read more guides

Written and reviewed with the help of AI. Editorial responsibility: APIbase. How AI is used here

Published: 2026-10-19Last updated: 2026-10-19