devutils-mcp-server

jwt_validate

Validate a JWT token's structure - verify its format, Base64URL encoding, JSON validity, and expiration. Signature verification is not performed.

Instructions

Validate the structure of a JWT. Checks format, Base64URL encoding, JSON validity, and expiration status. Does NOT verify the cryptographic signature.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "token": "<token>"
    },
    "name": "jwt_validate"
  }
}

Input Schema

Name	Required	Description	Default
`token`	Yes	The JWT string to validate

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Mar 24, 2026

TDQS

A4/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Describes what it checks and what it doesn't, but does not disclose output format (boolean, object, error?) given no annotations and no output schema. Adequate but leaves some behavior unspecified.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Single sentence, no unnecessary words, front-loaded with purpose and key constraints. Efficiently communicates core functionality.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple one-parameter validation tool, description covers what is validated and what is not. Missing output specification but overall complete for basic understanding.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Adds meaning beyond schema by listing specific validations performed on the token parameter. Schema only describes 'token' as JWT string; description fills in validation details.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

Description clearly states it validates JWT structure, enumerates specific checks (format, Base64URL, JSON, expiration), and explicitly notes it does not verify cryptographic signature, distinguishing it from signature verification tools.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Implies usage for structural validation, but does not explicitly name alternatives or specify when not to use. Mentions signature is not verified but doesn't point to jwt_decode or other tools for that.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.