# agentread /changes — URL Change Monitor

> agentread /changes — URL Change Monitor is a paid API for AI agents from agentread.midi-thumb.workers.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-31).

Checks whether a previously-fetched URL has changed since a baseline was established, returning a diff verdict or null if unchanged.

## Facts

- Endpoint: POST https://agentread.midi-thumb.workers.dev/changes?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-31
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agentread-changes-url-change-monitor-4ec1a762
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_yQJBtRY_F00cQKcwJpPeX

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 agentread-changes-url-change-monitor-4ec1a762 -d '<json body>'
```

Example prompt: Keep an eye on that product page for me — if anything changes from what you last saw, let me know right away.

## When to prefer this

Use this endpoint when you need to detect whether a URL's content has changed since a previous check, especially for pages that returned 403, 429, empty body, or JS-only shells when fetched directly. Prefer this over general-purpose scrapers when change detection (not full content extraction) is the primary goal, or when the target URL has previously blocked your fetches.

## Known failure modes

- URL is unreachable or permanently blocked — returns a verdict explaining why it cannot be read
- First call establishes baseline so 'changed' is always null on initial check
- Rate limits or anti-bot measures may prevent content retrieval, returning an explanatory verdict
- URL returns empty or JavaScript-shell page — may result in baseline_chars of 0 or a verdict string
- Invalid input schema (missing 'type' field) returns a validation error

## How this service works

Read a URL your own fetch failed on and get the page text back, or a verdict explaining why it cannot be read. Built for agents that just got a 403, 429, empty body or JS shell.

## Output

Returns a JSON object with: 'changed' (boolean or null if indeterminate), 'first_check' (boolean indicating whether this is the first baseline capture), and 'baseline_chars' (integer count of characters in the stored baseline). On first check, changed is null and the baseline is established.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "const": "http"
    },
    "method": {
     "const": "POST"
    }
   },
   "additionalProperties": true
  },
  "output": {
   "type": "object",
   "additionalProperties": true
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "changed": null,
  "first_check": true,
  "baseline_chars": 171
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agentread-changes-url-change-monitor-4ec1a762/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentread.midi-thumb.workers.dev](https://www.zero.xyz/host/agentread.midi-thumb.workers.dev/llms.txt)