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

Annotations already cover readOnly, idempotent, and non-destructive traits. The description adds valuable context: it requires an API key and counts toward quota, and it states that an empty result is a valid outcome. These are behavioral details beyond what annotations provide, so it earns a high score without contradicting the annotations.

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 is two sentences with no wasted words. The core action is front-loaded, and the additional caveats (auth, quota, empty result) are succinctly appended. It is appropriately sized for the tool's simplicity.

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 tool with one parameter, no output schema, and full annotation coverage, the description covers essential operational context: it mentions auth and quota constraints and warns about valid empty results. It does not explain return format, but that is not required given the simple retrieval nature. It is complete enough for correct invocation.

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 schema fully documents the single parameter 'word' with a description. The description's mention of 'English headword' slightly reinforces but adds no new meaning beyond the schema. Since schema coverage is 100%, the baseline is 3, and the description does not compensate further.

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 action ('Retrieve') and the resource ('available related-word data for an English headword'). It is specific enough to distinguish from generic lookup tools, though it does not explicitly name alternatives like explore_graph, so it loses a point for not differentiating among siblings.

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 gives no guidance on when to use this tool versus alternatives. It does not mention when not to use it, nor does it reference sibling tools or conditions that would select this over others. The only hint is 'available related-word data' which implies intent, but no explicit routing or exclusions.

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