{
  "product": "watch",
  "what": "A standing re-check of one citation or one package version.",
  "why": "A one-off lookup answers what was true when you asked. A watch keeps asking, and tells you when the answer changes: a retraction, a new advisory, a yanked version.",
  "price_usd": 0.5,
  "price_base_units": "500000",
  "credits": 10,
  "term_days": 30,
  "cadence_hours": 24,
  "buy_http": "POST /watch {\"kind\":\"citation\",\"query\":\"10.1038/nature12373\"} with a pack code; or {\"kind\":\"package\",\"package\":\"express@4.18.2\",\"ecosystem\":\"npm\"}",
  "buy_mcp": "Call the watch_add tool on the paid MCP door, US$0.5 a watch on the per-call rail.",
  "read": "GET /watch/<watch_id> with the token the purchase returned, as `authorization: Bearer <token>`.",
  "stop": "POST /watch/<watch_id>/stop with the same token. Unused days are not refunded.",
  "events": [
    "citation: retracted, notice_withdrawn, record_changed",
    "package: advisory_added, yanked, deprecated, record_changed"
  ],
  "webhook": "Optional: send an https URL at purchase and each change is POSTed to it as JSON. The event is recorded and its receipt issued whether or not the webhook is reachable.",
  "receipts": "The purchase answer carries a signed receipt for the first check, and every recorded change carries its own."
}