{
  "schema_version": "lvl-knowledge-lesson-v1",
  "id": "path-x402-01-canary-purchase-walkthrough",
  "category": "path",
  "path_ids": [
    "build-first-x402-service"
  ],
  "title": "Canary purchase walkthrough (concept + optional live)",
  "summary": "Use a $0.05 skill as a practice loop so the first real failure is cheap.",
  "body": "## Why a canary\n\nBefore an agent spends $25 on a pack, it should prove: wallet on Base, gas, USDC transfer, unlock JSON parse, re-redeem.\n\n## Conceptual walkthrough\n\n1. Read free outline for `agent-x402-first-buy`  \n2. Request 402 challenge  \n3. Confirm `maxAmountRequired` equals $0.05 in atomic USDC (50000)  \n4. Transfer exact amount to `payTo`  \n5. POST proof; persist sealed files offline  \n6. Re-POST same txHash to confirm idempotent redownload  \n\n## Optional live practice\n\nYou may run the real $0.05 unlock. It is **not required** to finish this path. The educational goal is the loop design.\n\n## Failure modes worth memorizing\n\n- Wrong chain (not Base)  \n- Wrong asset (ETH instead of USDC)  \n- Amount off by rounding  \n- Unlock too fast before confirmation  \n\n## Takeaway\n\nCanaries turn payment systems into learnable, testable loops.",
  "concepts": [
    "canary-purchase",
    "base-usdc",
    "first-buy"
  ],
  "related_skills_optional": [
    {
      "skill_id": "agent-x402-first-buy",
      "name": "Agent x402 First Buy",
      "price_usd": 0.05,
      "price_label": "$0.05 / unlock",
      "summary": "$0.05 start-here: prove your agent can complete HTTP 402 → Base USDC → sealed pack unlock on lvlltd.com.",
      "outline": "https://lvlltd.com/skills/agent-x402-first-buy/outline.json",
      "challenge": "https://lvlltd.com/api/pay?skill=agent-x402-first-buy",
      "listing": "https://lvlltd.com/listings/agent-x402-first-buy/",
      "available": true,
      "optional": true,
      "label": "optional_implementation"
    }
  ],
  "sort_order": 10,
  "estimated_minutes": 10,
  "last_updated": "2026-07-22T12:00:00.000Z",
  "freshness": {
    "last_updated_at": "2026-07-22T12:00:00.000Z",
    "days_since_update": 0,
    "band": "fresh",
    "score_0_100": 95,
    "label": "Fresh",
    "display": "Fresh · updated 2026-07-22 (0d ago)"
  },
  "integrity": {
    "knowledge_free": true,
    "skills_optional": true,
    "note": "This lesson is complete without purchasing any skill."
  },
  "related_bundles_optional": [],
  "url": "https://lvlltd.com/learn/lessons/path-x402-01-canary-purchase-walkthrough/",
  "updated_at": "2026-07-22T21:10:40.587Z"
}