# Agent402 UK JWT Decoder

> Agent402 UK JWT Decoder is a paid API for AI agents from agent402.co.uk, paid per call via x402, $0.001/call, status down (last checked 2026-09-14).

Decodes a JWT token's header and payload without verifying the signature, for debugging OIDC and agent tokens mid-task.

## Facts

- Endpoint: POST https://agent402.co.uk/v1/utils/jwt/decode
- Price: $0.001/call
- Payment: x402
- Status: down
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent402-uk-jwt-decoder-7c474065
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_T9jrkGUks02OoROhyAXJO

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 agent402-uk-jwt-decoder-7c474065 -d '<json body>'
```

Example prompt: Can you decode this JWT for me so I can see what's in the header and payload — I don't need signature verification, just want to inspect the claims: eyJhbGciOiJSUzI1NiIsImtpZCI6ImFiYyJ9.eyJzdWIiOiJ1c2VyXzEyMyIsImV4cCI6MTcwMDAwMDAwMH0.signature

## When to prefer this

Use this endpoint when an AI agent needs to inspect JWT claims mid-task without access to the signing key or secret, purely for debugging or routing decisions. Prefer this over full JWT verification endpoints when you explicitly do not need (or cannot perform) signature validation — for example, inspecting an OIDC token's sub, exp, or scopes to decide next steps in a workflow. Do not use this for security-sensitive authentication decisions, as signature verification is not performed.

## Known failure modes

- Malformed or non-JWT string input causes a parse error response
- Token with missing segments (not three dot-separated parts) will fail to decode
- Network or payment (x402) errors may prevent the call from completing
- Empty token field returns an error, not a decoded result

## How this service works

Don't burn tokens on deterministic work. Go/no-go jobs first: payout preflight, text firewall (PII/secrets), budget check — then rails, calendars, finmath. x402 USDC on Base. UK + global. agent402.co.uk — not agent402.tools. $0.001–$0.002 USDC on Base. No API keys.

## Output

Returns a JSON object containing the decoded JWT header and payload as key-value maps, a flag indicating whether a signature component is present, and a validity field. Does not verify the signature cryptographically — treats the token as untrusted data for inspection only.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "valid": true,
  "payload": {
   "sub": "1234567890"
  },
  "signature_present": false
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent402-uk-jwt-decoder-7c474065/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent402.co.uk](https://www.zero.xyz/host/agent402.co.uk/llms.txt)