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JWT Decoder API

br0ski777/jwt-decoder-x402

This is a decoder for JSON Web Tokens with an x402 micropayment layer baked in. It exposes tools to inspect JWT headers, payloads, claims, and expiry timestamps without needing to paste tokens into random websites. The repository is pretty bare, just TypeScript source and config files, so you're connecting to a remote endpoint at jwt-decoder.api.klymax402.com rather than running it locally. The x402 integration means you're paying per decode operation, which is an unusual model for what's typically a free utility. Reach for this if you're already in an x402 payment flow and need JWT inspection without context switching, but for casual debugging you'd probably just use jwt.io.

tool
1
transport
SSE
last updated
May 16, 2026
View on GitHub

Tools

1 tools

Public tool metadata for what this MCP can expose to an agent.

security_decode_jwtUse this when you need to decode and inspect a JWT token without verifying its signature. Returns the full header, payload, and expiration status. 1. header -- algorithm (RS256, HS256, etc.) and toke1 params

Use this when you need to decode and inspect a JWT token without verifying its signature. Returns the full header, payload, and expiration status. 1. header -- algorithm (RS256, HS256, etc.) and toke

Parameters* required
tokenstring
The JWT token to decode (format: header.payload.signature)

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Readme

JWT Decoder API

MCP Server x402 License: MIT

Decode and inspect JWT tokens without verification. Extracts header, payload, claims, expiry, and signature algorithm. Pay-per-call via x402 (USDC on Base L2) -- no API key, no signup, no rate-limit wall.

Part of the klymax402 marketplace -- 100 x402 micropayment APIs for AI agents, one wallet, USDC on Base.

Quickstart -- MCP

Add to your MCP client config (Claude Desktop, Cursor, ElizaOS, etc.):

{
  "mcpServers": {
    "jwt-decoder": {
      "url": "https://jwt-decoder.api.klymax402.com/mcp"
    }
  }
}

Quickstart -- HTTP (x402)

curl -X POST "https://jwt-decoder.api.klymax402.com/api/decode" \
  -H "Content-Type: application/json" \
  -d '{"token":"..."}'
# -> 402 Payment Required, with an x402 payment challenge in the response body

View the full README on GitHub

Details

Repository
github.com/br0ski777/jwt-decoder-x402
Website
github.com/Br0ski777/jwt-decoder-x402
Transport
SSE
Registry
MCP registry, active

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