---
skill_id: add-x402-usdc-checkout
evaluation: free
price_usd_full: 9.99
challenge: https://lvlltd.com/api/pay?skill=add-x402-usdc-checkout
outline: https://lvlltd.com/skills/add-x402-usdc-checkout/outline.json
standards: x402, ERC-7857
---

# Free sample — Add x402 USDC Checkout to Your Site

**Skill ID:** `add-x402-usdc-checkout`  
**Full unlock:** $9.99 USDC via x402 on Base  
**Challenge:** https://lvlltd.com/api/pay?skill=add-x402-usdc-checkout  
**Outline JSON:** https://lvlltd.com/skills/add-x402-usdc-checkout/outline.json

## Summary

Ship the same Base USDC x402 pay → verify → sealed unlock pattern LVL runs on lvlltd.com, swarm, and music — challenge, receipt, and unlock routes without inventing volume.

## When to use

- You want micropayment checkout on Base USDC without SaaS billing
- You run a skill, media, or API market and need HTTP 402 challenges
- You need a reusable pattern proven on lvlltd.com / swarm / music

## Decision criteria (buy vs skip)

- You need this when: You want micropayment checkout on Base USDC without SaaS billing
- You get capability: 402 challenge JSON templates (v1 and v2 fields)
- Budget fits: full unlock is $9.99 USDC on Base
- You can automate unlock via HTTP 402 without a browser
- You only need teaser/outline first — sealed src/ops stay locked until payment

## Outline (preview)

1. Declare price, payTo, asset (USDC on Base 8453) in a 402 challenge body with x402Version and x402_version
2. Serve free evaluation (outline/sample) before payment
3. Accept on-chain USDC transfer to payTo; verify receipt on Base
4. Unlock sealed payload only after verification; re-download with same tx
5. Publish proof only from confirmed ledger — never invent volume

## Capabilities (preview)

- 402 challenge JSON templates (v1 and v2 fields)
- Base USDC constants and payTo wiring checklist
- Human MetaMask and agent X-PAYMENT unlock paths
- Honesty/ledger notes for public metrics

## What you get after payment

- SKILL.md (teaser public)
- agent-install.json (public meta)
- src/index.js (stub public; full after unlock)
- Full sealed: src/, schemas/, ops/* (when present) after verified X-PAYMENT

## Agent buy path (zero human UI)

```
GET  https://lvlltd.com/skills/add-x402-usdc-checkout/outline.json
GET  https://lvlltd.com/api/pay?skill=add-x402-usdc-checkout   → HTTP 402
# transfer maxAmountRequired USDC to payTo on Base
POST https://lvlltd.com/api/pay
  X-PAYMENT: {"txHash":"0x…","skill":"add-x402-usdc-checkout"}
# response.sealed_pack.files = full pack
```

## Sample excerpt

# Add x402 USDC Checkout to Your Site

**Price:** $9.99 USDC  
**Category:** Commerce  
**Version:** 1.0  
**Protocols:** x402, ERC-7857  
**Tags:** x402, usdc, base, checkout, commerce, payments, merchant, integration  

## Summary

Ship the same Base USDC x402 pay → verify → sealed unlock pattern LVL runs on lvlltd.com, swarm, and music — challenge, receipt, and unlock routes without inventing volume.

## Description

Package of the working HTTP 402 → Base USDC → verify → unlock flow used in production across the LVL fleet. Includes challenge response shape (x402Version + x402_version), payTo/USDC contract constants, client MetaMask path notes, agent POST X-PAYMENT path, and honesty rules (never invent unlocks).

## When to use

- You want micropayment checkout on Base USDC without SaaS billing
- You run a skill, media, or API market and need HTTP 402 challenges
- You need a reusable pattern proven on lvlltd.com / swarm / music

## After purchase (lvlltd.com)

1. Pay USDC on Base via x402 to the treasury
2. POST `/api/pay` with `X-PAYMENT: {"txHash","skill":"add-x402-usdc-checkout"}`
3. Receive `sealed_pack.files` (code + docs)
4. Install: `node scripts/install-unlocked-pack.mjs unlock.json ./skills`
5. `import { createSkill } from './skills/add-x402-usdc-checkout/src/index.js'`

## Standards

- x402 micropayments (Base USDC / USDbC)
- ERC-7857 sealed iNFT ownership record (marketplace unlock ≠ runtime design)
- Operational packages ship as sealed pack files after verified payment

## Safety

- No secrets, private keys, or exploit content
- Human escalate on high blast-radius actions
- Not legal, tax, medical, or financial advice