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

With no annotations provided, the description carries the full burden. It discloses the critical behavioral trait that no signature verification occurs, and it describes the return shape (header, payload, standard claims, expiry status) in detail. It omits minor operational details like rate limits or security caveats, but the essential behavior is clear.

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 sentences, each earning its place: the first states the core action and a key differentiator, the second enumerates the return values, and the third gives the usage trigger. It is front-loaded and free of redundancy.

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 simple, read-only decoding utility with complete input schema coverage and no output schema, the description provides everything needed: the action, what it does not do, the output contents, and the usage scenario. No meaningful gaps remain for an agent to call it correctly.

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%, so both the 'token' and 'locale' parameters are fully documented in the schema. The description adds no parameter-level information beyond what the schema already provides, which is acceptable given the high coverage.

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 states a specific verb ('Decode') and resource ('JWT'), and immediately clarifies the scope by specifying it does not verify the signature. This distinguishes it from any hypothetical verify tool and tells the agent exactly what the operation does.

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?

It gives a clear usage context: 'Use this when a user pastes a JWT and wants to inspect its contents.' No alternative tools exist among the siblings for JWT inspection, so explicit when-not guidance is unnecessary; the context is sufficient.

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