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

readOnlyHint=true already covers the safety profile, so the bar is lower, and the description still adds meaningful context: the data source (annual securities report), the unit of all amounts (yen), the fact that both current and prior-year carrying amounts are returned, and the presence of aggregates. Gaps remain around empty results for companies with no strategic holdings and record-volume/pagination behavior.

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 purpose and field list are well front-loaded, but the body is padded: the full Japanese translation restates the English verbatim, and two separate paragraphs explain ISO 8601 date formatting for a tool with only two parameters. The date-time formatting note is boilerplate that does not change how an agent calls this tool.

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?

With no output schema, the description carries the full return-value burden and discharges it by naming each returned field plus the aggregation dimensions and currency. A three-file-level question about strategic holdings can be answered or routed correctly from this text alone.

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% and both parameters are documented there, including the 4-digit ticker example and the YYYY-MM pattern with the omit-for-latest default, so the baseline is 3. The description adds only indirect meaning, tying fiscalPeriod to annual securities report coverage rather than explaining fiscal-period edge cases (e.g., non-March year ends).

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 opening question states the exact resource and its scope: shares the company holds for strategic (non-investment) purposes, explicitly excluding pure investment holdings. It then enumerates the returned fields (issue name, shares held, carrying amount current/prior year, holding purpose) and the aggregates by purpose and listing status. An agent can distinguish this from holder-side siblings such as get_major_shareholders or get_large_holders without opening any schema.

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?

Usage is implied rather than stated: the annual-securities-report framing and the strategic-vs-pure-investment split signal when this tool applies, and the schema notes that omitting fiscalPeriod yields the latest report. However, no sibling tool is named as an alternative, and there is no explicit when-not-to-use guidance (e.g., use get_major_shareholders for who owns the company).

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