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

With no annotations, the description carries the burden of behavioral disclosure. It mentions the required API ID and the output format (English-keyed records). However, it does not specify whether partial name searches return multiple results, pagination behavior, or error conditions. It covers core behavior but leaves some operational details unstated.

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 two sentences, front-loaded with the main action and search criteria, then the requirement. No filler; every clause adds information. It is concise and well-structured.

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 lookup tool with two parameters and no output schema, the description covers the essential context: what it does, what it returns, and a key prerequisite. It lacks details on result limits or multiple matches, but for a simple lookup this is acceptable. The requirement note is particularly helpful.

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% for both parameters, so the schema already describes each field. The description adds value by clarifying that the two parameters are alternatives ('or'), which is not explicit in the schema. It also reinforces the 13-digit format and Japanese language requirement, providing practical guidance.

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 states a specific verb ('Look up') and a precise resource ('Japanese corporation'), and names the two search keys (partial name or 13-digit corporate number). It also distinguishes the tool from siblings by specifying the domain (corporations vs. law/statistics).

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 clearly states the prerequisite (a free National Tax Agency application ID) and implies usage for corporate lookups. It does not need to exclude siblings because they cover different domains. No explicit when-not-to-use is given, but the context is clear enough.

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