jwt_decode
Decode JWT payload and header (no signature verification).
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| token | Yes |
Decode JWT payload and header (no signature verification).
| Name | Required | Description | Default |
|---|---|---|---|
| token | Yes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description bears full burden. It explicitly states 'no signature verification', which is a key behavioral trait. However, it does not mention other relevant behaviors like the absence of validation checks.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is a single sentence with no unnecessary words. It is front-loaded and efficient.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool has no output schema, the description should clarify the return value (decoded payload and header) and possibly the format. It does not, leaving agents without key information.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, and the description adds no meaning to the 'token' parameter beyond its type. No format or constraints are explained.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the verb 'Decode' and the resource 'JWT payload and header', and distinguishes from sibling tools by noting 'no signature verification'. This makes the purpose unambiguous.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description implies use for decoding only, but does not explicitly state when to use versus alternatives like jwt_verify or jwt_sign. No when-not or alternative guidance is provided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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