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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds substantial behavioral context beyond those: it searches across Japanese/English/kana/EDINEC/ticker, returns industry/listing status/fiscal year end/corporate number, uses the official FSA list of ~11,000 filers, and requires no API key. The example also reveals expected output shape. No contradiction with annotations.

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?

Three sentences with no filler: the core purpose is front-loaded, the search/return capabilities are summarized efficiently, and the example, scope, and auth requirement are packed into the final sentence. Every sentence earns its place.

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 that there is no output schema, the description compensates by listing the returned fields and showing an explicit output example. Combined with high schema coverage for parameters and strong annotations for safety, the agent has everything needed to select and invoke this tool correctly.

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 the baseline is 3, but the description goes beyond the schema by adding 'kana' as a searchable query form and by providing a concrete example mapping 'Toyota' to E02144 / 7203. It does not need to re-explain the limit or listed_only parameters since the schema already documents them fully.

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 and resource: 'Resolve a Japanese company to its EDINET code and securities code from the FSA's official EDINET filer list.' It also positions the tool as 'the lookup every other EDINET call needs,' which distinguishes it from sibling tools like edinet_company_filings and edinet_list_filings without opening their schemas.

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 when to use it: as the prerequisite lookup for 'every other EDINET call.' It also adds a key access condition, 'Needs no API key,' and provides a concrete query example that makes the intended usage immediately clear.

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