# Stall-Row URL Change Detection Recheck

> Stall-Row URL Change Detection Recheck is a paid API for AI agents from stall-row-production.up.railway.app, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-29).

Probes a monitored URL (x402 resource or web page) without paying it and returns BASELINE, UNCHANGED, or CHANGED with a field-by-field diff against the last recorded state.

## Facts

- Endpoint: POST https://stall-row-production.up.railway.app/v1/recheck?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/stall-row-url-change-detection-recheck-1f7ae38f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_yzof1VvqEokT0eQtz1wxh

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 stall-row-url-change-detection-recheck-1f7ae38f -d '<json body>'
```

Example prompt: Check watch ID 'watch_abc123' using pack 'pack_xyz789' for the URL https://api.example.com/resource — tell me whether it's BASELINE, UNCHANGED, or CHANGED and show me exactly what fields differ from the last check.

## When to prefer this

Choose this endpoint when running scheduled agent loops that need to detect changes on x402 resources or web pages before spending money or attention on them. It is ideal when you want a cheap, stateful diff ($0.004–$0.005 per check) against a persisted baseline rather than fetching and comparing content yourself. Prefer it over generic web scrapers when you specifically need price, payTo, asset, or schema-level diffs on x402-compatible resources.

## Known failure modes

- Invalid or unreachable URL returns an error with no status
- Unknown watch_id may fail to find prior state, falling back to BASELINE
- Expired or exhausted pack_id returns a payment-required or quota-exceeded error
- Malformed input schema returns a 400-level validation error
- Target URL returning non-standard responses may produce incomplete diffs

## How this service works

Change detection for anything with a URL, built for monitoring loops: probe one x402 resource or web page WITHOUT paying it and answer BASELINE, UNCHANGED, or CHANGED with a field-by-field diff (price, asset, payTo, schema, page body) against the last check for that watch. Use this when an agent runs on a schedule and needs to know what changed before spending money or attention. Watch and pack state persist across redeploys on the service volume. Packs: $1 for 250 checks on one endpoint.

## Output

Returns a status of BASELINE (first check, establishes initial snapshot), UNCHANGED (no differences detected), or CHANGED (differences found), along with a field-by-field diff covering price, asset, payTo, schema, and page body changes compared to the last stored state for that watch ID.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string"
  },
  "pack_id": {
   "type": "string"
  },
  "watch_id": {
   "type": "string"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/stall-row-url-change-detection-recheck-1f7ae38f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from stall-row-production.up.railway.app](https://www.zero.xyz/host/stall-row-production.up.railway.app/llms.txt)