# PennyRail JWT Verify HMAC

> PennyRail JWT Verify HMAC is a paid API for AI agents from pennyrail.vercel.app, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-15).

Verifies a JWT token using HMAC signature validation and returns the verification result

## Facts

- Endpoint: POST https://pennyrail.vercel.app/api/p/skill/jwt.toolkit--jwt-verify-hmac
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/pennyrail-jwt-verify-hmac-a26e7c70
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UuYsqsQTFpyS2HtpO0G2G

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 pennyrail-jwt-verify-hmac-a26e7c70 -d '<json body>'
```

Example prompt: Can you verify this JWT token for me using HMAC — the token is eyJhbGciOiJIUzI1NiJ9.eyJ1c2VySWQiOiIxMjMifQ.abc123 and the secret is 'mysecretkey'?

## When to prefer this

Use this endpoint when you need a lightweight, pay-per-call HMAC JWT verification without standing up your own auth infrastructure. Particularly useful for agents that need one-off or low-volume JWT validation without managing a full identity service. Best for HS256/HS384/HS512 HMAC-signed tokens where you hold the shared secret.

## Known failure modes

- Invalid or malformed JWT token — returns error indicating bad token format
- Wrong HMAC secret provided — signature mismatch error
- Expired JWT — verification fails with expiry error
- Unsupported algorithm specified — returns unsupported algorithm error
- Missing required input fields — returns validation error
- Payment failure or insufficient USDC balance — 402 payment required error

## How this service works

Machine-readable settlement service

## Output

Returns a JSON object indicating whether the JWT signature is valid, along with the decoded token payload and any relevant claims if verification succeeds, or an error/failure indicator if the token is invalid, expired, or tampered with.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object",
 "additionalProperties": true
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/pennyrail-jwt-verify-hmac-a26e7c70/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from pennyrail.vercel.app](https://www.zero.xyz/host/pennyrail.vercel.app/llms.txt)