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

The annotation readOnlyHint=true already declares the non-destructive nature, and the description adds the 'verify and decode' behavior. However, it does not disclose details like error behavior on invalid signatures or whether the decoded payload is returned as a whole, which would be useful for debugging. With the annotation covering safety, a score of 3 is appropriate.

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 consists of two short sentences, front-loaded with the primary action ('Verify and decode a JWT') followed by the usage context. Every word earns its place; there is zero redundancy or 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 tool with no output schema, the description sufficiently conveys the core purpose and use case. It does not detail return values or error handling, but the simplicity of the tool reduces the need for such information, making the description reasonably complete.

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 input schema has 100% coverage: the single parameter 'token' is described as 'JWT token to decode', which is exactly what the description implies. The description adds no additional meaning beyond the schema, so the baseline of 3 is used.

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 tool's function: 'Verify and decode a JWT.' It uses a specific verb ('verify') and resource ('JWT'), and the sibling tool dev_jwt_sign makes the contrast between signing and verifying explicit, distinguishing this tool from its most likely alternative.

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 provides a clear usage context: 'Use when debugging authentication tokens.' This implies the tool is for inspection/validation rather than creation. It does not explicitly mention alternatives, but the sibling dev_jwt_sign naturally signals the complementary use case, so the guidance is adequate.

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