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

Annotations only declare readOnlyHint=true, so the description must carry the rest, and it does add a real behavioral trait: results may include preferred/other class shares with 5-digit codes flagged isPreferredShare: true, and the agent should select the 4-character common-stock code. It does not say how it handles multiple name matches, no-match cases, or what fields a hit returns, which keeps it below 5.

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 English portion is front-loaded and efficient, leading with the lookup keys and then the routing rule. The Japanese sentence is a near-verbatim translation of the same content (only the isPreferredShare clause is re-stated), which is duplicated payload rather than added information.

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 simple two-parameter read tool with no output schema, the definition covers the key ambiguity (preferred shares) but omits what a match actually returns and how limit affects the result set. The gap is moderate rather than severe, since the tool is otherwise narrow and predictable.

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 only 50% (only query is documented, limit is not), but the description compensates for the query parameter by clarifying it accepts either a ticker code or a name in Japanese or English, and by explaining the 5-digit preferred-share codes that can surface. The limit parameter is left to its schema defaults/min/max with no guidance on its use, so the compensation is partial.

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 gives a specific verb plus resource ('Find a Japanese listed company') and names both accepted lookup keys (ticker code or Japanese/English name). It is clearly separable from siblings such as search_edinet_code or list_stocks, which do not take a name/ticker query in this way.

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?

It states an explicit routing rule: 'Use this first when the user names a company but you do not know its ticker code,' which tells the agent when this tool is the entry point. It does not name competing tools (e.g. search_edinet_code) or state when not to use it, so it stops short of full alternative coverage.

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