# Slidingbox URL Drift Witness

> Slidingbox URL Drift Witness is a paid API for AI agents from drift.slidingbox.ai, paid per call via x402, $0.5/call, status down (last checked 2026-10-13).

Monitors a URL for changes by comparing each new check against all prior checks, detecting differences in status, redirects, content type, page sections, and loaded scripts (including PCI DSS 11.6.1 script-change detection).

## Facts

- Endpoint: POST https://drift.slidingbox.ai/v1/drift/watch?utm_source=zero.xyz
- Price: $0.5/call
- Payment: x402
- Status: down
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/slidingbox-url-drift-witness-8d68a3c5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_VwShSY4LETsajQ3UtPJdF

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 slidingbox-url-drift-witness-8d68a3c5 -d '<json body>'
```

Example prompt: Set up drift monitoring on https://shop.example.com/checkout — check it every hour, send change alerts to https://agent.example.net/hooks/drift, and flag if any scripts or redirects change compared to what was seen before.

## When to prefer this

Choose this endpoint when you need ongoing, automated monitoring of a specific URL for any form of change — especially when PCI DSS 11.6.1 compliance requires detecting script-set mutations on payment pages. It is ideal when you want webhook-driven alerts rather than polling yourself, need cross-caller historical comparison (not just your own baseline), and want lightweight drift metadata (not a full page copy). Prefer it over generic uptime monitors when script-level change detection and redirect drift are important.

## Known failure modes

- Invalid or unreachable URL returns an error
- Malformed callback URL causes registration failure
- Expired watch_id results in no further checks or callbacks
- Network timeout when fetching the target URL yields incomplete drift data
- First check always returns no drift (baseline establishment)
- Unsupported URL scheme or blocked domain may return an error

## How this service works

Has this page changed since it was last checked? Compares a URL with every earlier check of it by any caller: status, redirect target, content type, which sections changed, and whether the set of scripts it loads changed (the check PCI DSS 11.6.1 asks payment-page operators to run). Returns what was observed and from where, never the page itself. A page's first check is free.

## Output

Returns a JSON object containing the watch_id (UUID), the number of prior checks performed against the URL, an HMAC secret for verifying X-Drift-Signature on incoming callbacks, the registered callback URL, the watch expiry timestamp, and the polling interval in seconds. Subsequent callbacks deliver drift details: which sections changed, whether the script set changed, redirect target shifts, status code changes, and the observation source.

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "url": "https://example.com/",
  "checks": 168,
  "secret": "<64 hex chars; verifies X-Drift-Signature on each callback>",
  "callback": "https://agent.example.net/hooks/drift",
  "watch_id": "5f0c2a4e-8d1b-4c3f-9e7a-2b6d8f1c0a93",
  "expires_at": "2026-09-26T10:00:00.000Z",
  "interval_seconds": 3600
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/slidingbox-url-drift-witness-8d68a3c5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from drift.slidingbox.ai](https://www.zero.xyz/host/drift.slidingbox.ai/llms.txt)