# HMAC Signature Generator

> HMAC Signature Generator is a paid API for AI agents from x402-gateway-production-1f21.up.railway.app, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-12).

Computes an HMAC signature for a given text and secret key using SHA-256 or SHA-512, delivered as a machine-payable x402 microservice.

## Facts

- Endpoint: POST https://x402-gateway-production-1f21.up.railway.app/hmac?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-12
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/hmac-signature-generator-4d2eb233
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_PWkDaC7J2DAeBFoYHbmd1

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-signature-generator-4d2eb233 -d '<json body>'
```

Example prompt: Compute an HMAC-SHA256 signature for the text 'order_id=42&amount=99.99' using the secret key 'mysecretkey123' so I can authenticate this webhook payload.

## When to prefer this

Choose this endpoint when you need a lightweight, pay-per-use HMAC computation without provisioning your own crypto infrastructure. Ideal for agents that occasionally need to sign or verify message payloads in automated pipelines, especially when using the x402 micropayment protocol for serverless, wallet-based billing. Prefer over self-hosted solutions when you want zero-maintenance cryptographic utilities billed at $0.001 USDC per call.

## Known failure modes

- Missing required 'text' or 'key' fields returns a validation error
- Unsupported algorithm value (anything other than sha256 or sha512) returns an enum validation error
- Text exceeding 250,000 characters or key exceeding 10,000 characters may be rejected
- Payment failure via x402 protocol results in a 402 Payment Required response
- Network timeout on the Railway deployment returns a 5xx error

## How this service works

Machine-payable x402 utilities for hashing, Base64, UUID generation, unit and timezone conversion, realtime crypto market data, webpage/document extraction, URL-to-Markdown, metadata, RAG ingestion and deterministic website change detection.

## Output

Returns a JSON response with an HMAC digest (signature) computed from the provided text and secret key using the specified algorithm (SHA-256 or SHA-512), along with a status field confirming the operation completed successfully.

## 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",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "type": "object",
     "required": [
      "text",
      "key"
     ],
     "properties": {
      "key": {
       "type": "string",
       "maxLength": 10000
      },
      "text": {
       "type": "string",
       "maxLength": 250000
      },
      "algorithm": {
       "enum": [
        "sha256",
        "sha512"
       ],
       "type": "string"
      }
     },
     "additionalProperties": false
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "status": "ready"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/hmac-signature-generator-4d2eb233/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-gateway-production-1f21.up.railway.app](https://www.zero.xyz/host/x402-gateway-production-1f21.up.railway.app/llms.txt)