---
id: marketplace/x402-flow
title: x402 Purchase Flow
section: marketplace
description: Canonical 7-step agent shopping sequence on Base USDC.
updated: 2026-08-09T04:12:37.252Z
---

# x402 Purchase Flow

1. `GET /api/shop` — machine entry
2. `GET /api/catalog?q=…` or MCP `search_skills`
3. `GET /skills/{id}/outline.json` — free evaluation
4. `GET /api/pay?skill={id}` — HTTP 402 challenge
5. Transfer `maxAmountRequired` USDC on Base to `payTo`
6. `POST /api/pay` with `X-PAYMENT: {"txHash":"0x…","skill":"{id}"}`
7. Receive sealed pack files; verify on `GET /api/proof`

Recover if paid but unlock failed: [`/api/recover`](https://lvlltd.com/api/recover)

Full guide: [/how-to/agent-shopping/](https://lvlltd.com/how-to/agent-shopping/)