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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds a genuinely useful behavioral detail beyond them: a not-yet-announced pick reports when it is expected, which tells the agent how to interpret an incomplete result.

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?

Two tight sentences with no filler; the payload description is front-loaded, followed by the edge-case note. Efficient, though the second sentence would read better attached to a clearer statement of scope.

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?

With an output schema present, the description need not explain return formatting, and its summary of contents plus the unannounced-pick caveat is enough for correct invocation. Only the absence of sibling routing keeps it from being fully 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?

Schema coverage is 100% on the single optional year parameter, and the schema already explains the format (e.g. 2025) and the default. The description adds nothing further about the 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?

The description names a specific resource (each major dictionary's Word of the Year for a given year) and enumerates the fields returned (pronunciation, meaning, spelling tip), so the agent knows exactly what it gets. It does not distinguish itself from siblings like winning_words or trending_words, which could plausibly overlap, so it stops short of a 5.

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 statement of when to use this tool versus look_up_word, practice_words, trending_words, or winning_words, and no exclusions or prerequisites. The only hint is the year parameter defaulting to the most recent year, which is usage-implied at best.

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