# x402 Utils – JWT Decoder

> x402 Utils – JWT Decoder is a paid API for AI agents from utils.kagurazaka.dev, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-29).

Decodes a JWT's header and claims, returning the algorithm, payload, expiry timestamp, and whether the token has already expired — without verifying the signature.

## Facts

- Endpoint: POST https://utils.kagurazaka.dev/v1/jwt?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-29
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-utils-jwt-decoder-25372b10
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_m2XPy7M-puwqQ2d9cnP3e

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 x402-utils-jwt-decoder-25372b10 -d '<json body>'
```

Example prompt: Can you decode this JWT for me and tell me what claims it has, what algorithm it uses, and whether it's already expired: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwiZXhwIjoxNzkyODg2NDAwfQ.signature

## When to prefer this

Choose this endpoint when you need to quickly inspect a JWT's contents, check its expiration, or extract claims without setting up a local JWT library. Ideal for debugging, automation pipelines, or when the signing secret is unavailable. Note: this does NOT verify the signature, so do not use it as a security gate — only for informational inspection.

## Known failure modes

- Malformed or non-JWT string returns a parse error
- Token with no 'exp' claim may omit expiration fields
- Signature is never verified — a tampered token will still decode successfully
- Missing 'token' field in the request body returns a validation error

## How this service works

Decode a JSON Web Token's header and claims, and say when it was issued, when it expires, whether it has expired and in how many seconds it will. The signature is not verified.

## Output

A JSON object containing the JWT's algorithm (e.g. HS256), the full decoded payload as a key-value map of claims, the expiration timestamp as a UTC ISO 8601 string, a boolean indicating whether the token is expired, and the number of seconds until expiry (negative if already expired).

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "token": {
   "type": "string",
   "description": "the JWT"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "expired": false,
  "payload": {
   "exp": 1792886400,
   "sub": "123"
  },
  "algorithm": "HS256",
  "expires_at": "2026-10-25T00:00:00.000Z"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-utils-jwt-decoder-25372b10/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from utils.kagurazaka.dev](https://www.zero.xyz/host/utils.kagurazaka.dev/llms.txt)