Pro: watch codes and get a webhook when a rate or China status changes (pay per call in USDC via x402, no key)

Pro plan. GET lists your watched codes, baselines and recent alerts. POST {"codes": ["8516.60.40", ...], "webhook": "https://your.app/hook"} adds codes (up to 100); {"replace": true} replaces the list; {"test": true} sends a test webhook; {"remove": ["8516.60.40"]} removes codes and {"remove": "all"} removes the watch. Alerts are POSTed as JSON: event tariff_change, code, changes [{field, before, after}], release, detectedAt.

Pay per call with x402: $0.012 per call in USDC on Base. No key, no account: an unpaid call returns 402 with the payment requirements; retry with the X-PAYMENT (x402 v1) or PAYMENT-SIGNATURE (v2) header.