# URL File Checksum

> URL File Checksum is a paid API for AI agents from intel.rallylive.ca, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-14).

Fetches a file at a given URL and returns its SHA-256, SHA-1, SHA-384, MD5 hex digests, SRI integrity string, byte size, content type, last-modified, ETag, and final redirected URL.

## Facts

- Endpoint: GET https://intel.rallylive.ca/dev/checksum-file
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/url-file-checksum-13eb20dd
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_cOUMSFg9bo9_vOy5ybzX-

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-file-checksum-13eb20dd
```

Example prompt: Can you get me the SHA-256, SHA-384 SRI string, and file size for the file at https://cdn.example.com/app.js so I can pin it for subresource integrity?

## When to prefer this

Use this endpoint when you need cryptographic checksums of a specific remote file for integrity verification, SRI pinning, or tamper detection, and the file is under 5 MB. It is uniquely suited for agents that need to verify download authenticity, generate subresource integrity hashes for web assets, or monitor remote files for silent changes — all in a single call that also returns HTTP metadata like ETag and last-modified.

## Known failure modes

- File exceeds 5 MB limit — endpoint returns an error indicating the file is too large
- URL is unreachable or returns a non-200 HTTP status — error with HTTP status code returned
- URL redirects to an inaccessible or private resource — final URL reported but checksums unavailable
- Content-Type indicates unsupported format — partial metadata may be returned
- Network timeout fetching the remote file — timeout error returned

## How this service works

Checksums of a file at a URL (up to 5 MB): SHA-256, SHA-1 and MD5-free SHA-384 hex digests, the SRI string (sha384-…), byte size, content type, last-modified and ETag, plus the final URL after redirects. Verify downloads, pin script integrity, detect silent changes. $0.01 per file.

## Output

Returns a JSON object containing hex digests for SHA-256, SHA-1, SHA-384, and MD5; the SRI string (sha384-…); the file's byte size; HTTP content-type; last-modified header value; ETag; and the final URL after any redirects. Covers files up to 5 MB.

## 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",
     "properties": {}
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/url-file-checksum-13eb20dd/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from intel.rallylive.ca](https://www.zero.xyz/host/intel.rallylive.ca/llms.txt)