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

Annotations already provide readOnlyHint and idempotentHint. Description adds that it only converts kana, not kanji, and returns kanji as-is, plus passport style. No contradictions.

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 sentences in English, Japanese, and a bolded warning. Front-loaded with key info. Very concise, but the bilingual format adds a little length.

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 complexity (2 params, output schema exists), description explains input constraints, output behavior, and call sequence. Output schema covers return values, so no need for more.

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%, so baseline is 3. Description adds context about space splitting, but schema already includes that. No significant additional meaning beyond 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?

Description clearly states 'Hepburn romanize Japanese names (katakana/hiragana) in passport style' and specifies input must be kana, not kanji. Distinguishes from sibling kanji.toKana by telling user to call that first for readings of kanji.

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?

Explicitly says 'Input must be katakana or hiragana — kanji is returned as-is and NOT converted. To get readings of kanji names, call kanji.toKana first.' This clearly defines when to use and when to use an alternative.

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