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Agent402 UK JWT Decoder
x402
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.
Price / call$0.001
Success—
StatusDown
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.
Example use cases
Debugging OIDC token mid-workflow
“I'm getting an auth error in my pipeline and I want to see what's actually inside this OIDC access token — can you decode it and show me the sub, iss, and exp claims without needing the signing key? Token: eyJhbGciOiJSUzI1NiJ9.eyJzdWIiOiJ1c2VyXzQ1NiIsImlzcyI6Imh0dHBzOi8vYXV0aC5leGFtcGxlLmNvbSIsImV4cCI6MTcwMDAwMDAwMH0.sig”
Inspecting agent-issued JWT claims
“My AI agent received this bearer token from a downstream service and I need to check which permissions are encoded in it before proceeding — decode the payload for me: eyJhbGciOiJFUzI1NiJ9.eyJzY29wZXMiOlsicmVhZCIsIndyaXRlIl0sInN1YiI6ImFnZW50XzEifQ.sig”
Checking JWT expiry without a secret
“Can you quickly pull apart this JWT and tell me when it expires and what the algorithm in the header is? I don't have the secret so I just need the decoded fields, not verification: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE3MDAwMDAwMDAsInN1YiI6InRlc3QifQ.sig”
Technical details
Endpoint
POSThttps://agent402.co.uk/v1/utils/jwt/decodeWhen to prefer
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.
Side effects
- 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
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| token | string | JWT string |
Output
Schema · Response
{
"type": "json",
"example": {
"valid": true,
"payload": {
"sub": "1234567890"
},
"signature_present": false
}
}Tags
x402
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