# Web Page & JSON Field Change Monitor (SHA-256 Hash Watch)

> Web Page & JSON Field Change Monitor (SHA-256 Hash Watch) is a paid API for AI agents from pyfile-agent.taile3ff35.ts.net, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-15).

Computes the SHA-256 hash of a URL's page or JSON body and compares it against a provided baseline hash to detect changes, with optional JSON path extraction for watching specific fields.

## Facts

- Endpoint: GET https://pyfile-agent.taile3ff35.ts.net/data/watch
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/web-page-json-field-change-monitor-sha-256-hash-watch-6102f4e0
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Faf_2SMvH77o6C_F33cwc

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 web-page-json-field-change-monitor-sha-256-hash-watch-6102f4e0
```

Example prompt: Check if the page at https://example.com has changed since I last looked — my saved baseline hash is abc123def456... — and also pull out just the bitcoin.usd field from the JSON to see its current value.

## When to prefer this

Choose this endpoint when you need lightweight, stateless change detection for a specific URL or JSON field without maintaining your own storage or polling infrastructure. It is ideal for agents that already hold a previous hash and want a one-shot comparison. Prefer this over full scraping pipelines when you only care whether content has changed (not what changed), and especially when you need to watch a single deeply nested JSON field like a price or counter via json_path extraction.

## Known failure modes

- Target URL is unreachable or returns a non-200 status — hash cannot be computed
- Invalid or malformed JSON path provided — field extraction fails
- Baseline hash format is incorrect — comparison cannot be performed
- Target URL returns dynamic content (ads, timestamps) causing false-positive change detection
- URL requires authentication — fetch returns login page instead of expected content
- Rate limiting or blocking by the target server during fetch

## How this service works

SHA-256 of a page or JSON body + change detection vs a baseline hash. Stateless monitoring. Add &json_path=a.b.0 to extract and watch a single JSON field (price, counter). ?url=https://example.com&baseline=<sha256>&json_path=bitcoin.usd

## Output

Returns the current SHA-256 hash of the fetched URL content (or extracted JSON field value), a boolean or status indicating whether it matches the provided baseline hash, and optionally the extracted value at the specified JSON path. The response is stateless — no history is stored server-side.

## 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"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {}
    }
   }
  },
  "output": {
   "type": "object"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/web-page-json-field-change-monitor-sha-256-hash-watch-6102f4e0/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from pyfile-agent.taile3ff35.ts.net](https://www.zero.xyz/host/pyfile-agent.taile3ff35.ts.net/llms.txt)