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

Annotations only declare readOnlyHint=true, so safety is already covered; the description adds genuinely useful behavior beyond that — the legal basis of the data, the fact that the response also carries a `consolidated` block, and an explicit warning that the two counts are not interchangeable. It does not describe edge cases such as a missing voting-rights section or how holder rows are ordered, which keeps it short of a 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 well ordered: source, contents, the critical non-subtraction warning, then the pointer to `consolidated`. However, every sentence is repeated verbatim in Japanese and the ISO 8601 / YYYY-MM-DD boilerplate is stated twice, roughly doubling length without adding information relevant to this tool's two non-datetime parameters.

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 two-parameter read lookup with no output schema, the description covers what the record contains, where in the filing it comes from, how it relates to the separately returned `consolidated` figures, and the most likely downstream misuse. An agent has everything needed to call it and interpret the result 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 description coverage is 100%, and the schema already explains the 4-digit ticker and that omitting `fiscalPeriod` yields the latest annual report, so the baseline of 3 applies. The description adds no further parameter meaning; its date-format notes concern returned values (and neither parameter is a date-time).

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 names a specific resource and its exact source: treasury shares from the annual securities report's voting-rights section, enumerating the disclosed sub-fields (own name, others' names, total, holder rows, ratio to issued shares, per-class issued shares). It explicitly contrasts this with the consolidated accounting count, so an agent cannot confuse it with the earnings-summary figures returned in `consolidated`.

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 the interpretive boundary sharply: this is Companies Act art. 308 voting-rights disclosure, and shares outstanding must not be derived by subtracting it from issued shares. It also points to where the consolidated counts actually live. It stops short of naming sibling tools (e.g. the key-metrics/earnings tools) by name, so selection among siblings is inferred rather than directed.

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