HALOWERK Price Change Callback Monitor

Use this endpoint when you need asynchronous, webhook-driven notification of price changes on a specific web page, rather than polling repeatedly yourself. It is ideal when you want to react to price movements in a specific direction (increase, decrease, or any) above a configurable minimum threshold, without building your own scraping and monitoring infrastructure. Prefer this over general web scraping endpoints when the goal is specifically price surveillance with callback delivery.

• Target URL is unreachable or returns non-200 status — monitoring cannot be established
• Price element not found or parseable on the target page — returns error indicating price extraction failure
• Callback URL is invalid or unreachable — notification delivery fails silently or returns error
• Idempotency key format invalid (must be 32-128 alphanumeric/dash/underscore chars) — 400 validation error
• Currency code not in ISO 4217 three-letter format — 400 validation error
• Previous value or minimum_change exceeds maximum of 1,000,000,000 — 400 validation error
• Payment not provided or insufficient USDC balance — 402 Payment Required