Security

JWT Inspector & Verifier

Decode a JWT (header + payload) with syntax highlighting, diagnose standard claims, and verify the signature with HS*/RS*/PS*/ES*/EdDSA keys — plus a tampered-token forgery demo

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Quick start

Call this tool from your code in three languages.

cURL

curl -X POST 'https://api.elysiatools.com/en/api/tools/jwt-inspector-verifier' \
  -H 'Content-Type: application/json' \
  -d '{"token":"eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkphbmUgRG9lZSIsImlhdCI6MTUxNjIzOTAyMn0.yo-bLjjeUhUPia17JiJbc2f1e0JXJIJAi4auivcB-IY","mode":"verify","secret":"demo-secret-2026","publicKey":"","forgePayload":"","clockSkew":0}'

API reference

Send a POST request with your inputs as JSON. File parameters require a separate upload first.

Endpoint

HTTP

POST https://api.elysiatools.com/en/api/tools/jwt-inspector-verifier

Parameters

Name	Type	Required	Description
token	textarea	Yes	—
mode	select	No	—
secret	text	No	—
publicKey	textarea	No	—
forgePayload	textarea	No	—
clockSkew

MCP integration

Add this tool to your Model Context Protocol server so AI agents can list and call it.

Server configuration

Add this block to your MCP client configuration:

mcp.json

{
  "mcpServers": {
    "elysiatools-jwt-inspector-verifier": {
      "name": "jwt-inspector-verifier",
      "description": "Decode a JWT (header + payload) with syntax highlighting, diagnose standard claims, and verify the signature with HS*/RS*/PS*/ES*/EdDSA keys — plus a tampered-token forgery demo",
      "baseUrl": "https://api.elysiatools.com/mcp/sse?toolId=jwt-inspector-verifier",
      "command": "",
      "args": [],
      "env": {},
      "isActive": true,
      "type": "sse"
    }
  }
}

List available tools

After connecting to the SSE endpoint, list the exposed tools:

tools/list

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/list"
}

Call this tool

Invoke the tool by its id, passing arguments built from its parameters:

tools/call

{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "jwt-inspector-verifier",
    "arguments": {
  "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkphbmUgRG9lZSIsImlhdCI6MTUxNjIzOTAyMn0.yo-bLjjeUhUPia17JiJbc2f1e0JXJIJAi4auivcB-IY",
  "mode": "verify",
  "secret": "demo-secret-2026",
  "publicKey": "",
  "forgePayload": "",
  "clockSkew": 0
}
  }
}

Chain multiple tools in one session with a comma-separated toolId list, e.g. /mcp/sse?toolId=png-to-webp,jpg-to-webp,gif-to-webp (max 20).

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