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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds useful context beyond that: the catalogue is internal and exceeds a hundred thousand words, and results include links and audio recordings. Return-field detail is partly redundant given an output schema exists.

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?

Purpose and resource are front-loaded in the opening clause, and the trailing sentence gives usage. The middle enumeration of every returned field is fairly long, though it does help the agent judge whether the tool fits the query.

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 one-parameter read-only lookup with a full output schema, the description covers what it does, what the source data is, and when to reach for it. No auth, pagination, or side-effect caveats are needed for a public catalogue read.

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?

There is a single parameter with 100% schema description coverage, including example words, so the schema fully carries parameter meaning. The description's mention of 'an English word' reinforces the expected input domain, but adds little beyond the schema.

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 and resource (look up an English word) and names the exact source catalogue with its scale. It is clearly distinguishable from the list-style siblings (trending_words, words_of_the_year, etc.), which browse collections rather than resolve a single word.

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 final sentence gives concrete usage contexts: checking a spelling and retrieving the clue types a speller may ask for in a bee. It does not explicitly name an alternative sibling or state when not to use it, so it stops short of a 5.

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