# util.beauty Crypto Signature Utility

> util.beauty Crypto Signature Utility is a paid API for AI agents from util.beauty, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Generates or verifies cryptographic signatures via a metered REST endpoint, payable per-request with USDC on Base or prepaid API keys.

## Facts

- Endpoint: POST https://util.beauty/v1/crypto/signature
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/util-beauty-crypto-signature-utility-00c884ca
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_4USBZakAlJN8E5g6zOauq

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 util-beauty-crypto-signature-utility-00c884ca -d '<json body>'
```

Example prompt: Sign this message — 'Hello, world!' — using my private key, and give me back the cryptographic signature I can use to prove ownership.

## When to prefer this

Choose this endpoint when you need a quick, pay-per-use cryptographic signing or verification operation without deploying your own crypto infrastructure. Ideal for AI agents or serverless workflows that occasionally need to sign messages or verify signatures, especially in web3 or API-auth contexts, without managing long-lived secrets or heavyweight SDKs.

## Known failure modes

- Invalid or malformed private key returns an error response with ok: false
- Unsupported signature algorithm causes a 400-level error
- Insufficient payment balance or invalid x402 payment header causes a 402 Payment Required response
- Malformed JSON body causes a 400 Bad Request
- Key/message mismatch during verification returns ok: false with a verification failure indicator

## How this service works

Metered web utilities for developers and AI agents: browser screenshot and PDF, crypto, DNS and net tools. Pay per request with x402 (USDC on Base) or prepaid API keys.

## Output

Returns a JSON object with ok (boolean), a utility identifier string, a unique requestId, the number of charged credits, and the computed signature or verification result in the response body.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "properties": {
  "input": {
   "type": "object",
   "properties": {
    "body": {
     "type": "object",
     "description": "JSON request body (see OpenAPI for the utility schema).",
     "additionalProperties": true
    }
   }
  },
  "output": {
   "type": "object",
   "properties": {
    "example": {
     "type": "object",
     "properties": {
      "ok": {
       "type": "boolean"
      },
      "utility": {
       "type": "string"
      },
      "requestId": {
       "type": "string"
      },
      "chargedCredits": {
       "type": "number"
      }
     },
     "additionalProperties": true
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "ok": true,
  "utility": "…",
  "requestId": "req_…",
  "chargedCredits": 1
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/util-beauty-crypto-signature-utility-00c884ca/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from util.beauty](https://www.zero.xyz/host/util.beauty/llms.txt)