{
  "id": "build-first-x402-service",
  "slug": "build-first-x402-service",
  "title": "Build your first x402 service",
  "audience": [
    "human",
    "agent"
  ],
  "level": "intermediate",
  "estimated_minutes": 60,
  "summary": "From first successful micropay loop to designing a merchant-safe paywall: challenges, exact amounts, re-redeem, and integrity checks.",
  "outcomes": [
    "Complete a $0.05 canary unlock mentally (and optionally for real)",
    "Design a 402 challenge with correct atomic USDC amount",
    "Avoid double-pay with idempotent redeem keys",
    "Verify sealed payload hashes after unlock"
  ],
  "lesson_ids": [
    "path-x402-01-canary-purchase-walkthrough",
    "path-x402-02-challenge-anatomy",
    "path-x402-03-idempotency-and-retries",
    "path-x402-04-sealed-pack-integrity",
    "path-x402-05-merchant-checklist"
  ],
  "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"
    },
    {
      "skill_id": "x402-retry-idempotency-kit",
      "name": "x402 Retry Idempotency Kit",
      "price_usd": 0.99,
      "price_label": "$0.99 / unlock",
      "summary": "Safe retries after flaky 402 unlocks without double-spend logic errors.",
      "outline": "https://lvlltd.com/skills/x402-retry-idempotency-kit/outline.json",
      "challenge": "https://lvlltd.com/api/pay?skill=x402-retry-idempotency-kit",
      "listing": "https://lvlltd.com/listings/x402-retry-idempotency-kit/",
      "available": true,
      "optional": true,
      "label": "optional_implementation"
    },
    {
      "skill_id": "sealed-payload-integrity-checker",
      "name": "Sealed Payload Integrity Checker",
      "price_usd": 3.99,
      "price_label": "$3.99 / unlock",
      "summary": "Verify data_hash matches delivered sealed content before trusting an unlock.",
      "outline": "https://lvlltd.com/skills/sealed-payload-integrity-checker/outline.json",
      "challenge": "https://lvlltd.com/api/pay?skill=sealed-payload-integrity-checker",
      "listing": "https://lvlltd.com/listings/sealed-payload-integrity-checker/",
      "available": true,
      "optional": true,
      "label": "optional_implementation"
    },
    {
      "skill_id": "gas-fee-forecaster-base",
      "name": "Gas Fee Forecaster (Base)",
      "price_usd": 0.49,
      "price_label": "$0.49 / unlock",
      "summary": "Estimate Base gas spend for a month of unlocks and agent txs.",
      "outline": "https://lvlltd.com/skills/gas-fee-forecaster-base/outline.json",
      "challenge": "https://lvlltd.com/api/pay?skill=gas-fee-forecaster-base",
      "listing": "https://lvlltd.com/listings/gas-fee-forecaster-base/",
      "available": true,
      "optional": true,
      "label": "optional_implementation"
    },
    {
      "skill_id": "x402-merchant-operating-system",
      "name": "x402 Merchant Operating System",
      "price_usd": 39,
      "price_label": "$39.00 / unlock",
      "summary": "End-to-end OS for running an x402 skill market: catalog, proof, disputes, and growth.",
      "outline": "https://lvlltd.com/skills/x402-merchant-operating-system/outline.json",
      "challenge": "https://lvlltd.com/api/pay?skill=x402-merchant-operating-system",
      "listing": "https://lvlltd.com/listings/x402-merchant-operating-system/",
      "available": true,
      "optional": true,
      "label": "optional_implementation"
    }
  ],
  "related_bundles_optional": [
    {
      "bundle_id": "bundle-x402-buyer-ops",
      "name": "x402 Buyer Ops Stack",
      "price_usd": 4.49,
      "savings_usd": 1.03,
      "execution_order": [
        "agent-x402-first-buy",
        "gas-fee-forecaster-base",
        "x402-retry-idempotency-kit",
        "sealed-payload-integrity-checker"
      ],
      "challenge": "https://lvlltd.com/api/pay?skill=bundle-x402-buyer-ops",
      "optional": true,
      "label": "optional_stack"
    }
  ],
  "featured": true,
  "sort_order": 20,
  "schema_version": "lvl-knowledge-path-v1",
  "lessons": [
    {
      "id": "path-x402-01-canary-purchase-walkthrough",
      "order": 1,
      "title": "Canary purchase walkthrough (concept + optional live)",
      "summary": "Use a $0.05 skill as a practice loop so the first real failure is cheap.",
      "estimated_minutes": 10,
      "concepts": [
        "canary-purchase",
        "base-usdc",
        "first-buy"
      ],
      "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)"
      },
      "url": "https://lvlltd.com/learn/lessons/path-x402-01-canary-purchase-walkthrough/",
      "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"
        }
      ],
      "related_bundles_optional": []
    },
    {
      "id": "path-x402-02-challenge-anatomy",
      "order": 2,
      "title": "Anatomy of a 402 challenge",
      "summary": "Which fields a client must read: amount, payTo, network, asset contract, skill binding.",
      "estimated_minutes": 9,
      "concepts": [
        "402-fields",
        "atomic-usdc",
        "skill-binding"
      ],
      "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)"
      },
      "url": "https://lvlltd.com/learn/lessons/path-x402-02-challenge-anatomy/",
      "related_skills_optional": [
        {
          "skill_id": "x402-receipt-normalizer",
          "name": "x402 Receipt Normalizer",
          "price_usd": 11.99,
          "price_label": "$11.99 / pack",
          "summary": "Normalize crypto/x402 receipts into ledger-ready payment events.",
          "outline": "https://lvlltd.com/skills/x402-receipt-normalizer/outline.json",
          "challenge": "https://lvlltd.com/api/pay?skill=x402-receipt-normalizer",
          "listing": "https://lvlltd.com/listings/x402-receipt-normalizer/",
          "available": true,
          "optional": true,
          "label": "optional_implementation"
        }
      ],
      "related_bundles_optional": []
    },
    {
      "id": "path-x402-03-idempotency-and-retries",
      "order": 3,
      "title": "Idempotency: never pay twice for one unlock",
      "summary": "Slow unlocks are not unpaid unlocks. Design attempt ledgers so agents do not double-transfer.",
      "estimated_minutes": 8,
      "concepts": [
        "idempotency",
        "retry-policy",
        "double-pay"
      ],
      "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)"
      },
      "url": "https://lvlltd.com/learn/lessons/path-x402-03-idempotency-and-retries/",
      "related_skills_optional": [
        {
          "skill_id": "x402-retry-idempotency-kit",
          "name": "x402 Retry Idempotency Kit",
          "price_usd": 0.99,
          "price_label": "$0.99 / unlock",
          "summary": "Safe retries after flaky 402 unlocks without double-spend logic errors.",
          "outline": "https://lvlltd.com/skills/x402-retry-idempotency-kit/outline.json",
          "challenge": "https://lvlltd.com/api/pay?skill=x402-retry-idempotency-kit",
          "listing": "https://lvlltd.com/listings/x402-retry-idempotency-kit/",
          "available": true,
          "optional": true,
          "label": "optional_implementation"
        }
      ],
      "related_bundles_optional": []
    },
    {
      "id": "path-x402-04-sealed-pack-integrity",
      "order": 4,
      "title": "Sealed packs and integrity checks",
      "summary": "Payment proves you paid. Hash checks prove the files match the listing claim.",
      "estimated_minutes": 8,
      "concepts": [
        "erc-7857",
        "data-hash",
        "sealed-pack"
      ],
      "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)"
      },
      "url": "https://lvlltd.com/learn/lessons/path-x402-04-sealed-pack-integrity/",
      "related_skills_optional": [
        {
          "skill_id": "sealed-payload-integrity-checker",
          "name": "Sealed Payload Integrity Checker",
          "price_usd": 3.99,
          "price_label": "$3.99 / unlock",
          "summary": "Verify data_hash matches delivered sealed content before trusting an unlock.",
          "outline": "https://lvlltd.com/skills/sealed-payload-integrity-checker/outline.json",
          "challenge": "https://lvlltd.com/api/pay?skill=sealed-payload-integrity-checker",
          "listing": "https://lvlltd.com/listings/sealed-payload-integrity-checker/",
          "available": true,
          "optional": true,
          "label": "optional_implementation"
        }
      ],
      "related_bundles_optional": []
    },
    {
      "id": "path-x402-05-merchant-checklist",
      "order": 5,
      "title": "Merchant checklist for an x402 skill market",
      "summary": "What operators must keep consistent: catalog, challenge, unlock, proof, and support truth.",
      "estimated_minutes": 10,
      "concepts": [
        "merchant-ops",
        "catalog-honesty",
        "cold-start"
      ],
      "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)"
      },
      "url": "https://lvlltd.com/learn/lessons/path-x402-05-merchant-checklist/",
      "related_skills_optional": [
        {
          "skill_id": "x402-merchant-operating-system",
          "name": "x402 Merchant Operating System",
          "price_usd": 39,
          "price_label": "$39.00 / unlock",
          "summary": "End-to-end OS for running an x402 skill market: catalog, proof, disputes, and growth.",
          "outline": "https://lvlltd.com/skills/x402-merchant-operating-system/outline.json",
          "challenge": "https://lvlltd.com/api/pay?skill=x402-merchant-operating-system",
          "listing": "https://lvlltd.com/listings/x402-merchant-operating-system/",
          "available": true,
          "optional": true,
          "label": "optional_implementation"
        },
        {
          "skill_id": "cold-start-catalog-bootstrapper",
          "name": "Cold-Start Catalog Bootstrapper",
          "price_usd": 7.99,
          "price_label": "$7.99 / unlock",
          "summary": "Launch play for a marketplace with zero sales history and empty social proof.",
          "outline": "https://lvlltd.com/skills/cold-start-catalog-bootstrapper/outline.json",
          "challenge": "https://lvlltd.com/api/pay?skill=cold-start-catalog-bootstrapper",
          "listing": "https://lvlltd.com/listings/cold-start-catalog-bootstrapper/",
          "available": true,
          "optional": true,
          "label": "optional_implementation"
        }
      ],
      "related_bundles_optional": []
    }
  ],
  "lesson_count": 5,
  "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)"
  },
  "urls": {
    "human": "https://lvlltd.com/learn/paths/build-first-x402-service/",
    "machine": "https://lvlltd.com/learn/paths/build-first-x402-service.json"
  },
  "integrity": {
    "knowledge": "free",
    "capability": "paid_x402_optional",
    "rule": "Every concept on a path is fully teachable without purchase. Skills are optional implementations, never required reading.",
    "display": "Learn free. Buy only if you want a ready-to-run sealed pack."
  },
  "updated_at": "2026-07-22T21:10:40.587Z"
}