# Sample — Add x402 USDC Checkout (60s)

## Live challenge (no payment)

```bash
curl -si "https://lvlltd.com/api/pay?skill=agent-x402-first-buy" | head -40
```

You should see **HTTP 402** with `x402Version` and `x402_version` on the body, plus `accepts[]` describing Base USDC.

## Free outline first

Always publish a free evaluation URL before charging. Example:

- Outline: `/skills/<id>/outline.json`
- Sample: `/skills/<id>/sample.md`

## Honesty

Confirmed unlocks only via a ledger you can open publicly (LVL uses `/api/proof`). Never invent volume.

## Learn more

- [/learn/x402-explained/](https://lvlltd.com/learn/x402-explained/)
- [/learn/agents-buy-skills-http/](https://lvlltd.com/learn/agents-buy-skills-http/)
- [/learn/buy-first-skill-metamask/](https://lvlltd.com/learn/buy-first-skill-metamask/)