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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, covering safety and idempotency. The description adds value by specifying the return fields (headword, common-ness, JLPT level, etc.) and input acceptances (kanji, kana, romaji, English). It does not cover potential rate limits or external API dependency, but for a simple lookup this is sufficient.

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 concise (3 sentences) and front-loaded with the core purpose. Every sentence provides essential information: what it does, what it returns, best use case, and accepted input formats. No wasted words.

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?

Given the tool's simplicity (single parameter, no output schema) and comprehensive annotations, the description fully covers the necessary context. It explains the input, output, and intended use, leaving no significant gaps for an agent to misinterpret.

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% for the single parameter 'word', with a detailed description. The main tool description reiterates the accepted input types ('kanji, kana, romaji, or English'), which adds no new information beyond the schema. Baseline score of 3 is appropriate as the description does not enhance parameter understanding significantly.

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 ('look up'), the resource ('a single Japanese or English word in the Jisho.org dictionary'), and the return format ('compact form... headword, common-ness, JLPT level, readings, meanings, parts of speech'). It distinguishes from sibling tools like 'search_words' by emphasizing single best match and compactness.

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 explicitly states the best use case: 'quick "what does this word mean / how is it read" questions'. It implicitly differentiates from broader searches (e.g., 'search_words' sibling) but does not mention specific scenarios when not to use or alternatives. This is adequate but not exhaustive.

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