# URL Change Fingerprint

> URL Change Fingerprint is a paid API for AI agents from base-agent-preflight.bytoken2023.workers.dev, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-13).

Generates a change-detection fingerprint for a public HTTP(S) URL to assess whether its content has been altered, along with a risk score and flags.

## Facts

- Endpoint: GET https://base-agent-preflight.bytoken2023.workers.dev/v1/x402/web/url-change-fingerprint
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/url-change-fingerprint-68849f3f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_p3KZTwWEfHCsV6niF0vzN

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 url-change-fingerprint-68849f3f
```

Example prompt: Can you fingerprint https://example.com/terms-of-service and tell me if the content has changed or looks risky — I want a risk score and any flags.

## When to prefer this

Use this endpoint when you need to detect whether a specific public web document has changed content or shows signs of tampering, particularly in autonomous agent workflows operating on Base where verifying the integrity of external URLs before acting on them is critical. Prefer this over generic HTTP fetch tools when you need a structured risk assessment alongside the fingerprint.

## Known failure modes

- URL is not reachable or returns non-200 status — endpoint may return an error or elevated risk flags
- URL does not match the required https?:// pattern — schema validation error
- URL exceeds 2048 character limit — rejected at input validation
- Target URL requires authentication or returns bot-protection page — fingerprint may be inaccurate or incomplete
- Payment not provided or insufficient — 402 Payment Required response

## How this service works

Machine-payable service intelligence for discovering, verifying, and monitoring identity, risk, authorization, execution-preflight, and evidence APIs before autonomous agents spend.

## Output

A JSON object containing a network identifier (e.g. eip155:8453), the product name 'url-change-fingerprint', an assessment object with a risk_level (e.g. 'low'), a numeric risk_score, and an array of flags indicating any detected issues with the URL's content or change state.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "pattern": "^https?://",
       "maxLength": 2048,
       "description": "Public HTTP(S) document URL to fingerprint."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "network": {
       "type": "string"
      },
      "product": {
       "type": "string"
      },
      "activity": {
       "type": "object"
      },
      "identity": {
       "type": "object"
      },
      "assessment": {
       "type": "object"
      },
      "provenance": {
       "type": "object"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "network": "eip155:8453",
  "product": "url-change-fingerprint",
  "assessment": {
   "flags": [],
   "risk_level": "low",
   "risk_score": 0
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/url-change-fingerprint-68849f3f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from base-agent-preflight.bytoken2023.workers.dev](https://www.zero.xyz/host/base-agent-preflight.bytoken2023.workers.dev/llms.txt)