# AgentResolver HMAC-SHA256 Signing

> AgentResolver HMAC-SHA256 Signing is a paid API for AI agents from agentresolver.vercel.app, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-18).

Computes an HMAC-SHA256 message authentication code for a given input string using a secret key

## Facts

- Endpoint: POST https://agentresolver.vercel.app/api/hmac-sha256
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-18
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agentresolver-hmac-sha256-signing-51aa5037
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_EtmzgJWh_3F7y0nWXFKzw

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 agentresolver-hmac-sha256-signing-51aa5037 -d '<json body>'
```

Example prompt: Compute an HMAC-SHA256 signature for the message 'order-id=12345&amount=99.99' using the secret key 'my-webhook-secret'.

## When to prefer this

Use this endpoint when you need a simple, pay-per-use HMAC-SHA256 computation without setting up a cryptographic library locally, or when running in an environment where native crypto is unavailable. It is ideal for lightweight agent workflows that occasionally need to sign payloads or verify data integrity without bundling crypto dependencies.

## Known failure modes

- Missing required field 'input' or 'secret' returns a 400 or validation error
- Empty string inputs may produce unexpected or zero-length results
- Invalid JSON body causes a parse error
- Payment not provided or insufficient results in a 402 Payment Required response

## How this service works

Verify an x402 endpoint before paying: live payTo, USDC quote, network, asset, resource binding, TLS and endpoint safety for $0.001 on Base or Solana.

## Output

Returns a JSON object containing the HMAC-SHA256 result string (typically hex-encoded), the encoding format used, the operation name ('hmac-sha256'), and the byte count of the input string.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "input": {
   "type": "string",
   "maxLength": 131072
  },
  "secret": {
   "type": "string",
   "maxLength": 4096,
   "minLength": 1
  }
 }
}
```

## Response schema (JSON Schema)

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

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agentresolver-hmac-sha256-signing-51aa5037/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentresolver.vercel.app](https://www.zero.xyz/host/agentresolver.vercel.app/llms.txt)