# Webwache Canonical Change Monitor

> Webwache Canonical Change Monitor is a paid API for AI agents from webwache.halowerk.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-22).

Passively fetches a public URL and evaluates a documented criterion to determine whether a monitored condition or change threshold has been met, returning observation, verdict, and evidence source.

## Facts

- Endpoint: POST https://webwache.halowerk.com/v1/canonical-change-monitor?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-22
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/webwache-canonical-change-monitor-923e1c6f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_PJxGCBZ7H-RPo4JXH-7nJ

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 webwache-canonical-change-monitor-923e1c6f -d '<json body>'
```

Example prompt: Check https://example.com/pricing to see if the pricing has changed since my last snapshot — use the baseline I captured yesterday and tell me whether the change threshold has been met, what the evidence is, and what you recommend I do next.

## When to prefer this

Use this endpoint when you need a passive, read-only evaluation of whether a public webpage meets a specific criterion or has changed relative to a baseline — without any login, form submission, or active interaction. It is ideal for automated monitoring workflows where you want a structured verdict plus evidence provenance rather than just a raw diff. Prefer it over general web scrapers when you need an opinionated yes/no verdict with documented limitations and a recommended action.

## Known failure modes

- Target URL is unreachable or returns a non-200 status — endpoint reports inability to fetch evidence
- Target URL requires authentication or is behind a paywall — endpoint notes this as a limitation and cannot evaluate
- Malformed or non-HTTP(S) URL provided — request rejected with validation error
- Target content is dynamically rendered JavaScript-only and cannot be passively parsed — limitation noted in response
- No meaningful change detectable due to anti-scraping measures — limitation reported in verdict

## How this service works

Canonical change monitor plan fetches current public evidence from the supplied target and evaluates the documented criterion. It returns the observation, threshold, verdict, exact evidence source, limitations and a mode-specific action. The check is passive: no login attempt, payload injection, exploit, purchase, form submission or load test is performed.

## Output

Returns a structured response containing: the observation (what was found at the target URL), the threshold being evaluated, a verdict (whether the criterion was met), the exact evidence source, any limitations of the passive check, and a mode-specific recommended action. The baseline and context labels provided in the request are echoed back unchanged.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "target": {
   "type": "string",
   "maxLength": 2048,
   "minLength": 3,
   "description": "Public HTTP(S) URL or domain to inspect. A bare domain is normalized to HTTPS."
  },
  "context": {
   "type": "object",
   "description": "Optional non-secret correlation labels returned unchanged only in the request lifecycle.",
   "maxProperties": 12,
   "additionalProperties": {
    "type": [
     "string",
     "number",
     "boolean",
     "null"
    ]
   }
  },
  "baseline": {
   "type": [
    "object",
    "null"
   ],
   "description": "Optional baseline returned by a previous snapshot call.",
   "additionalProperties": true
  },
  "compare_url": {
   "type": "string",
   "maxLength": 2048,
   "minLength": 3,
   "description": "Optional public comparison URL. Used by change and monitoring services."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/webwache-canonical-change-monitor-923e1c6f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from webwache.halowerk.com](https://www.zero.xyz/host/webwache.halowerk.com/llms.txt)