---
id: overview/core-concepts
title: Core Concepts
section: overview
description: x402, free evaluation, sealed packs, proof ledger, swarm.
updated: 2026-08-09T04:12:37.252Z
---

# Core Concepts

## x402

HTTP **402 Payment Required** challenges carry amount, payTo, asset, and network. Clients pay on-chain, then POST proof to unlock.

## Free evaluation

Every curated skill exposes free:

- `/skills/{id}/outline.json`
- `/skills/{id}/sample.md`
- `/skills/{id}/assets/*` (preview, schema, checklist)

## Sealed packs

Full runtimes live under lock until verified payment. Teasers may exist under `/sealed/`; full files arrive only after unlock.

## Proof ledger

Confirmed unlocks only: [`/api/proof`](https://lvlltd.com/api/proof). Quiet is honesty.

## Hub products

Marketplace · Labs (create/pack journey) · Swarm · Studio · NFTs · Network dashboard · Upload (open market).