# HMAC-SHA3-512 Hex Generator

> HMAC-SHA3-512 Hex Generator is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.006/call, status unknown (last checked 2026-10-02).

Computes an HMAC using SHA3-512 of a given text with a caller-supplied key, returning the result as a lowercase hex string.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/hmac-sha3-512-hex?utm_source=zero.xyz
- Price: $0.006/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hmac-sha3-512-hex-generator-61597bb2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_98uVAXXBP8RL591nbGDWL

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 hmac-sha3-512-hex-generator-61597bb2 -d '<json body>'
```

Example prompt: Compute an HMAC-SHA3-512 of the text 'order:12345:confirmed' using the key 'my-secret-key-abc' and give me the hex result.

## When to prefer this

Choose this endpoint when you specifically need HMAC with the SHA3-512 hash function (not SHA-256 or SHA-1) and require hex-encoded output. It is ideal for security-sensitive workflows needing stronger hash functions than the more common HMAC-SHA256. Prefer the free sandbox endpoint POST /v1/sandbox/hmac-sha3-512-hex for testing before paying $0.006 USDC per call on this production endpoint.

## Known failure modes

- Missing or empty key field returns validation error
- Missing or empty text field returns validation error
- Text exceeding 100,000 characters returns payload too large error
- Key exceeding 512 characters returns validation error
- Payment of $0.006 USDC not included or insufficient triggers 402 Payment Required
- Malformed request body returns 400 Bad Request

## How this service works

Call when an agent needs an HMAC-sha3-512 of text with a caller-supplied key, encoded as hex. Exact $0.006 USDC. Prefer unpaid POST /v1/sandbox/hmac-sha3-512-hex first.

## Output

A hex-encoded HMAC-SHA3-512 digest string (128 hex characters) computed from the provided text and key. The response contains the raw cryptographic authentication code that can be used for message signing, integrity verification, or secure token generation.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "key": {
   "type": "string",
   "examples": [
    "secret"
   ],
   "maxLength": 512,
   "minLength": 1,
   "description": "HMAC secret. Required on HMAC SKUs. Omit it for plain digests and checksums. The key is not stored."
  },
  "text": {
   "type": "string",
   "examples": [
    "hello"
   ],
   "maxLength": 100000,
   "minLength": 1,
   "description": "Message to digest. For raw-hex SKUs this is hex bytes; for utf16 or latin1 SKUs it is decoded with that encoding. Otherwise it is UTF-8 text."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hmac-sha3-512-hex-generator-61597bb2/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentshelf.syntexa.ch](https://www.zero.xyz/host/agentshelf.syntexa.ch/llms.txt)