# Unveil Prompt Injection Scanner (URL)

> Unveil Prompt Injection Scanner (URL) is a paid API for AI agents from unveil.x402utils.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-10-11).

Fetches a URL and scans the retrieved content for hidden prompt injection attacks targeting AI agents, returning severity-graded findings with SHA-256 evidence hashes but never the matched text itself.

## Facts

- Endpoint: GET https://unveil.x402utils.workers.dev/v1/scan-url?utm_source=zero.xyz
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-11
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/unveil-prompt-injection-scanner-url-359162c9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_p6TbKnfPe8XQORmXBUgiS

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 unveil-prompt-injection-scanner-url-359162c9
```

Example prompt: Before you summarize that GitHub README at https://github.com/someuser/somerepo/blob/main/README.md, run it through Unveil's URL scanner to check for any hidden prompt injection, invisible Unicode smuggling, or instructions secretly addressed to you.

## When to prefer this

Choose this endpoint when your AI agent is about to consume content from an untrusted or user-supplied URL and you want to guard against prompt injection before processing. It is distinct from text-based scanning because it fetches the remote resource itself, including rendered HTML, comments, and CSS-hidden elements that a raw text scan would miss. Prefer it over generic content-moderation APIs when the threat model specifically involves adversarial instructions targeting AI agents rather than human-facing harmful content.

## Known failure modes

- URL exceeds 1 MB page size limit — request rejected
- URL is unreachable or returns non-2xx status — fetch error returned
- Invalid or non-HTTP(S) URL provided — schema validation error
- Payment not completed via x402/USDC — 402 Payment Required response
- Method not in allowed enum (GET, HEAD, DELETE) — validation error

## How this service works

Scan untrusted text or URLs for hidden prompt injection before an AI agent reads them: invisible Unicode, tag-character smuggling, bidi overrides, terminal escapes, instructions in HTML comments or CSS-hidden elements, secret-exfiltration requests, text addressed to AI readers. Matched text is never returned (sha256 only). Paid per call via x402, USDC on Base.

## Output

A JSON object containing a top-level verdict ('safe', 'suspicious', or 'dangerous'), a counts object with low/medium/high finding tallies, and a findings array. Each finding includes the rule ID (e.g. UNV002), a human-readable title, line and column, severity, evidence length, and a SHA-256 hash of the matched text — the actual matched content is never returned.

## 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",
      "HEAD",
      "DELETE"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "url"
     ],
     "properties": {
      "url": {
       "type": "string",
       "description": "http(s) URL of a page/README/issue to fetch and scan (max 1 MB)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "counts": {
   "low": 0,
   "high": 1,
   "medium": 0
  },
  "verdict": "dangerous",
  "findings": [
   {
    "line": 1,
    "rule": "UNV002",
    "title": "Unicode tag-character smuggling",
    "column": 6,
    "detail": "16 tag characters decode to a withheld payload",
    "severity": "high",
    "evidence_length": 41,
    "evidence_sha256": "3f1c…"
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/unveil-prompt-injection-scanner-url-359162c9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from unveil.x402utils.workers.dev](https://www.zero.xyz/host/unveil.x402utils.workers.dev/llms.txt)