# ChangeCheck

> ChangeCheck is a paid API for AI agents from changecheck-mainnet-production.up.railway.app, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-11).

Detects and summarizes meaningful changes on a public webpage compared to a previous snapshot, returning a confidence-scored summary of what changed.

## Facts

- Endpoint: POST https://changecheck-mainnet-production.up.railway.app/change?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/changecheck-f9c85a5c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_XWCxhpZg9hw8wbzarugAg

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 changecheck-f9c85a5c -d '<json body>'
```

Example prompt: Check if this webpage has changed since my last snapshot — here's the URL https://example.com/announcements and here's the previous content I saved: 'Closing date: 20 October 2024'. Tell me what changed and whether it's a meaningful update.

## When to prefer this

Choose ChangeCheck when you need to detect and summarize meaningful changes on a specific public webpage, especially when you have a prior snapshot to compare against. It is ideal for monitoring deadlines, announcements, policy pages, product listings, or any text-heavy public page where semantic understanding of what changed matters — not just a byte-level diff. Prefer it over generic web scrapers when you need a confidence-scored, human-readable summary of changes rather than raw content.

## Known failure modes

- URL is not publicly accessible or returns a non-200 status — endpoint may fail to retrieve content
- previous_content is malformed or truncated — may reduce comparison accuracy and confidence score
- Webpage uses heavy JavaScript rendering — static fetch may miss dynamically loaded content
- Payment failure or insufficient USDC balance — request rejected before processing
- URL points to a binary file or non-text content — change detection may be unreliable

## How this service works

Paid x402 API that detects meaningful changes on public webpages.

## Output

Returns a JSON object with: a boolean 'changed' indicating whether the page differs from the baseline, a human-readable 'summary' of what changed, a 'confidence' score (0–1) reflecting certainty of the analysis, a 'material_change' boolean indicating whether the change is substantive, a 'baseline_created' boolean indicating if this was the first call establishing a baseline, and an 'important_changes' array listing specific notable changes detected.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "format": "uri",
   "description": "Public webpage to check for changes"
  },
  "previous_content": {
   "type": "string",
   "description": "Optional previous snapshot. Omit on the first call to create a baseline."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "changed": true,
  "summary": "The closing date moved from 20 October to 27 October.",
  "confidence": 0.96,
  "material_change": true,
  "baseline_created": false,
  "important_changes": [
   "Closing date changed"
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/changecheck-f9c85a5c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from changecheck-mainnet-production.up.railway.app](https://www.zero.xyz/host/changecheck-mainnet-production.up.railway.app/llms.txt)