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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds the critical behavioral caveat that no signature verification occurs and enumerates what is computed (expiry status, seconds until expiry, human-readable claims), which is real added context beyond the structured data.

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?

One dense sentence with the most important qualifier (no signature verification) placed early and the returned fields listed after. Zero filler.

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?

No output schema exists, and the description compensates by naming the returned signals (expiry status, seconds until expiry, human-readable iat/nbf/exp). It omits error behavior for malformed or truncated tokens, a minor gap for a single-parameter decoding utility.

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 the single parameter is fully documented there, including the 'Bearer ' prefix stripping behavior. The description adds nothing about the token parameter, so the baseline 3 applies.

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 (JWT, header and payload) and immediately scopes it with 'without verifying the signature,' which is the single most decision-relevant qualifier for a JWT tool. No sibling tool overlaps, so differentiation is unnecessary.

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?

Usage is implied rather than stated: 'without verifying the signature' hints at inspection/debugging scenarios, but there is no explicit when-to-use or when-not-to-use guidance, and no alternative tool is named (none exists among siblings). Adequate but leaves the trigger condition to inference.

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