# HMAC-MD5 Hex Digest (agentshelf.syntexa.ch)

> HMAC-MD5 Hex Digest (agentshelf.syntexa.ch) is a paid API for AI agents from agentshelf.syntexa.ch, paid per call via x402, $0.009/call, status unknown (last checked 2026-10-01).

Computes an HMAC-MD5 authentication code over supplied text using a caller-provided secret key, returning the result as a lowercase hexadecimal string.

## Facts

- Endpoint: POST https://agentshelf.syntexa.ch/v1/hmac-md5-hex?utm_source=zero.xyz
- Price: $0.009/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hmac-md5-hex-digest-agentshelf-syntexa-ch-d957a80d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Nkg8ow2cdD0T10NUxYWEy

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-md5-hex-digest-agentshelf-syntexa-ch-d957a80d -d '<json body>'
```

Example prompt: Calculate the HMAC-MD5 hex digest of the text 'Hello, World!' using the secret key 'mysecretkey123'.

## When to prefer this

Choose this endpoint when you need an HMAC-MD5 keyed message authentication code returned as hexadecimal — specifically when MD5 is required (e.g. for compatibility with a legacy system, AWS S3 request signing, or an API that mandates HMAC-MD5). Prefer the free sandbox endpoint POST /v1/sandbox/hmac-md5-hex for testing. Use sibling endpoints if you need a different hash algorithm (SHA-512, SHAKE128) or a different encoding (base64, base32).

## Known failure modes

- Empty or missing 'key' field returns a validation error
- Empty or missing 'text' field returns a validation error
- Key exceeding 512 characters is rejected
- Text exceeding 100,000 characters is rejected
- Payment of $0.009 USDC not provided or failing results in 402 Payment Required
- Malformed JSON body returns 400 Bad Request

## How this service works

Call when an agent needs an HMAC-md5 of text with a caller-supplied key, encoded as hex. Exact $0.009 USDC. Prefer unpaid POST /v1/sandbox/hmac-md5-hex first.

## Output

A JSON response containing the hex-encoded HMAC-MD5 digest string computed from the provided text and key. The output is a fixed-length 32-character lowercase hexadecimal string representing the 128-bit HMAC value.

## 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-md5-hex-digest-agentshelf-syntexa-ch-d957a80d/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)