# JWT Claims Validator MCP for AI Agents MCP

> JWT Claims Validator lets you inspect JSON Web Tokens to see if they've expired or are not yet valid. It decodes the payload and checks timestamps like expiration and not-before claims against the current time without needing a full signature verification. Use it to catch bad tokens before your agent attempts an authenticated API call.

## Overview
- **Category:** developer-tools
- **Price:** Free
- **Endpoint:** https://edge.vinkius.com/vk_preview_P6u7uYZqm7b1xlgsX1l9T96GkSQC7KF63hyJ7LU0/mcp
- **Tags:** jwt, security, auth, validation, token

## Description

When you are building automated workflows, passing an expired token to an API is a waste of resources. You end up with failed requests, error logs, and unnecessary latency. This MCP lets your agent peek inside the token payload to see if it is still usable before ever attempting an authenticated call. It handles the heavy lifting of decoding the Base64Url format and comparing timestamps against the clock. You can use this as a quick pre-flight check in any sequence involving authentication. By connecting through Vinkius, you get immediate access to this validation logic alongside thousands of other specialized tools. It is about making your agent smarter by teaching it to recognize a dead token before it even hits the network.

## Tools

### validate_jwt
Checks if a JWT's structure is correct and its claims are still active. It identifies expired or not-yet-valid tokens instantly.

## Prompt Examples

**Prompt:** 
```
Is this JWT still valid? eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
```

**Response:** 
```
The token is **valid**. 

* **Status:** Active
* **Expiration:** In the future
* **Claims:** All required claims are present.
```

**Prompt:** 
```
Check if this token has expired: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
```

**Response:** 
```
The token is **expired**. The expiration claim indicates it expired on January 1st, 2024.
```

**Prompt:** 
```
Does this token look like a properly formatted JWT?
```

**Response:** 
```
Yes, the structure is valid. It contains a correctly formatted header, payload, and signature segment.
```

## Capabilities

### Check token expiration
See if a token is still active or already dead.

### Inspect payload structure
Confirm the token follows the correct format.

### Verify timestamp validity
Check not-before and issued-at claims against the current time.

### Decode Base64Url payloads
Read the data inside the token without manual decoding.

### Identify malformed tokens
Detect structural errors in a JWT string immediately.

## Use Cases

### Token Expiry Detection
An engineer asks their agent to check a list of tokens, and the agent flags which ones need refreshing.

### Automated Security Audits
A security professional provides a batch of intercepted JWTs to see if any have been active past their intended window.

### CI/CD Pipeline Validation
A DevOps engineer uses an agent to verify that newly generated service tokens are valid before deploying them to production.

## Benefits

- Reduce API errors by catching expired tokens early in your workflow.
- Save bandwidth by avoiding failed authenticated requests.
- Speed up debugging with instant payload decoding.
- Automate pre-flight security checks in your agent's sequence.
- Avoid unnecessary 401 Unauthorized responses from your backend services.

## How It Works

The bottom line is you stop sending dead tokens to your APIs.

1. Provide a JWT string to your AI client.
2. The MCP decodes the payload and compares timestamps to the current system clock.
3. You get a clear answer on whether the token's claims are currently active.

## Frequently Asked Questions

**How can I use JWT Claims Validator to prevent API errors?**
Use it as a pre-flight check in your agent's workflow to catch expired tokens before they hit your backend.

**Does JWT Claims Validator verify the cryptographic signature of a token?**
No, this MCP only inspects the payload and timestamps. You still need to verify the signature using your standard authentication logic.

**Can I check the expiration date of a token with JWT Claims Validator?**
Yes, it specifically checks the expiration claim against the current time to tell you if a token is still active.

**Will JWT Claims Validator work in Claude or Cursor?**
Yes, any MCP-compatible client like Claude, Cursor, or Windsurf can use this tool to inspect tokens.

**What happens if I provide an invalid string to JWT Claims Validator?**
The tool will identify that the structure is not a valid JWT and notify your agent of the formatting error.

**Does this tool verify the cryptographic signature of the JWT?**
No. This tool focuses on structural and claim-based validation (like expiration) without performing expensive cryptographic signature verification.

**What claims are checked during validation?**
The tool checks the `exp` (expiration), `nbf` (not before), and `iat` (issued at) claims to ensure the token is currently valid.

**Can I use this with Claude Desktop or Cursor?**
Yes, you can connect this MCP server to Claude Desktop, Cursor, VS Code, Windsurf, and any other MCP-compatible client via Vinkius Edge.