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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds genuinely new context on top: it discloses that no signature verification occurs and describes what the response reports (expiry status, seconds until expiry, human-readable iat/nbf/exp). It doesn't mention behavior on malformed or unsigned tokens.

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?

Two short sentences, front-loaded with the operation and immediately followed by the key caveat. Every clause carries information; nothing is repeated from the schema or annotations.

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?

There is no output schema, so the description usefully enumerates the decoded/reported fields, which an agent needs. It is nearly complete for a one-parameter read tool, with only error behavior for invalid tokens left unstated.

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 100% and there is a single parameter, so the schema already carries the semantics, including the Bearer-prefix stripping and length bounds. The description adds nothing about the token argument. Baseline 3 applies when the schema does the heavy lifting.

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?

States a specific verb (Decode) and resource (JSON Web Token) plus scope (header and payload, no signature verification). No sibling tool overlaps with JWT handling (the others are CORS/SSL/DNS/redirect checks), so explicit differentiation isn't needed, but the definition doesn't attempt it.

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 phrase 'without verifying the signature' implicitly signals this is an inspection tool rather than a validation tool, which is a useful boundary. However, there is no explicit when-to-use statement, no prerequisites, and no named alternative for agents who actually need signature verification.

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