# HALOWERK Price Change Callback Monitor

> HALOWERK Price Change Callback Monitor is a paid API for AI agents from handel.halowerk.com, paid per call via x402, $0.006/call, status unknown (last checked 2026-10-29).

Registers a callback URL to be notified when a webpage's displayed price changes by a specified amount or direction

## Facts

- Endpoint: POST https://handel.halowerk.com/v1/price-change-callback?utm_source=zero.xyz
- Price: $0.006/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-price-change-callback-monitor-d1f33b9e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_lR6QDyDMqWzLfmGD1fcNi

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability halowerk-price-change-callback-monitor-d1f33b9e -d '<json body>'
```

Example prompt: Watch https://shop.example.com/product/widget for any price decrease from the current price of 49.99 USD, with a minimum change of 2.00, and call back my webhook at https://myapp.example.com/price-alert when it happens.

## When to prefer this

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.

## Known failure modes

- 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

## How this service works

HALOWERK handelswerk — bezahlte Endpunkte nach x402. Preise in USDC auf Base Mainnet.

## Output

An acknowledgment that the price watch has been registered. When the monitored page's price changes in the specified direction by at least the minimum threshold, the provided callback_url receives a POST notification with the detected price change details.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType"
   ],
   "properties": {
    "type": {
     "const": "http"
    },
    "method": {
     "const": "POST"
    },
    "bodyType": {
     "const": "json"
    },
    "schemaUrl": {
     "type": "string",
     "format": "uri"
    },
    "exampleUrl": {
     "type": "string",
     "format": "uri"
    }
   },
   "additionalProperties": true
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "const": "json"
    },
    "schemaUrl": {
     "type": "string",
     "format": "uri"
    },
    "exampleUrl": {
     "type": "string",
     "format": "uri"
    }
   },
   "additionalProperties": true
  }
 },
 "additionalProperties": true
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/halowerk-price-change-callback-monitor-d1f33b9e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from handel.halowerk.com](https://www.zero.xyz/host/handel.halowerk.com/llms.txt)