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

With no annotations, the description carries the full burden and does a good job: it discloses that the signature is NOT verified, that the token is never transmitted externally (a privacy guarantee), and the cost of 1 credit per call. It omits behavior on malformed/expired tokens and the exact return shape, which keeps it short of a 5.

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?

Three short sentences, each earning its place: purpose, the critical non-verification/privacy caveat, and cost. Front-loaded with the action and free of 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?

For a single-parameter, read-only decoder with no output schema, the description covers what gets decoded (header, claims, expiry), the signature-verification limit, privacy, and cost. Only minor gaps remain around error handling and the precise decoded response shape.

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?

The single 'token' parameter has 0% schema description coverage, so the schema only supplies type and length bounds. The description implies the expected input is a raw JWT via the phrase 'JSON Web Token', but adds no format or encoding guidance (e.g., compact JWS string) beyond that.

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 claims), plus the additional expiry check. No sibling tool does anything similar, so the agent can identify this unambiguously from the name and description alone.

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?

There is no explicit when-to-use guidance or named alternative, but the scope boundary 'Does not verify the signature' implicitly tells the agent when this tool is and isn't appropriate. Usage is implied rather than spelled out.

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