JWT Decoder — Inspect Claims, Expiry & Algorithm

JWT token decoder API for AI agents.

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What it can do

  • Security Decode Jwt: 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, H

What data it sees

Do you need an account

No: the server works without sign-in

JWT token decoder API for AI agents. Decode and inspect JSON Web Tokens without verification: extract header (algorithm, type), payload (claims, issuer, audience), expiry timestamp, and signature info.

Tools: security_decode_jwt.

Use this for debugging authentication flows, inspecting token claims, or verifying token structure. IMPORTANT: This decodes without verifying — for security validation, verify signatures server-side.

Returns: {header, payload, claims, expiresAt, algorithm}. No API key required — x402 micropayment $0.001/call on Base L2.

How to connect

How to connect JWT Decoder — Inspect Claims, Expiry & Algorithm to Claude

The server address to paste into Claude settings:

https://jwt-decoder--axel-belfort.run.tools

  1. Open Claude (claude.ai or the desktop app).
  2. Go to Settings → Connectors.
  3. Click Add custom connector.
  4. Paste the server address copied below into Remote MCP server URL and click Add.
  5. In a chat, click + → Connectors and switch the new connector on.

Custom connectors are available on Free, Pro, Max, Team and Enterprise plans (Free is limited to one). On Team and Enterprise an organization Owner adds the connector first under Organization settings → Connectors.

Authorization

After you click Add, a sign-in window for the service opens. Sign in with your own account and approve access. Claude never sees your password.

How to connect JWT Decoder — Inspect Claims, Expiry & Algorithm to ChatGPT

The server address to paste into ChatGPT settings:

https://jwt-decoder--axel-belfort.run.tools

  1. Open ChatGPT in a browser (chatgpt.com). A Plus, Pro, Business, Enterprise or Edu plan is required.
  2. Turn on developer mode once: Settings → Apps → Advanced settings → Developer mode.
  3. Open Settings → Connectors and click Create.
  4. Fill in the form: Name (anything), Description (one line about what the service does), MCP server URL (copy it below).
  5. Under Authentication choose OAuth if the service requires sign-in, otherwise None. Click Create.
  6. In a new chat open + → Apps/Connectors and enable the connector.

OpenAI has renamed this section before (Connectors → Apps/Plugins). If the label differs, search settings for "developer mode". On Business/Enterprise workspaces an admin must allow custom connectors first.

Authorization

On first use ChatGPT opens the service's sign-in window. Sign in and approve access.

How to connect JWT Decoder — Inspect Claims, Expiry & Algorithm to Cursor

The server address to paste into Cursor settings:

https://jwt-decoder--axel-belfort.run.tools

Fastest: click Open in Cursor below and confirm the prompt.

Manually:

  1. In Cursor open Settings → Cursor Settings → MCP and click Add new global MCP server.
  2. Paste the JSON copied below into ~/.cursor/mcp.json (per project: .cursor/mcp.json in the repo root).
  3. Save the file. The server appears in the MCP list; authorize it there if asked.

Authorization

If the service needs sign-in, an authorize button appears next to the server in the MCP list.

Server tool list (1)

Raw names from tools/list. Only developers need these.

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 toke