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

Annotations only declare readOnlyHint=true, and the description adds genuinely non-derivable behavior: a 10-token cost, a 10-year cap per request, split/share-count adjustment semantics, and that from/to are interpreted in JST. Return format/pagination is not described, but the added context is substantial beyond the annotation.

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?

Front-loaded with the core definition and formula, then defaults, limits, and timezone caveats. Dense and mostly waste-free; the bilingual duplication and the repeated JST note cost a little, but it is justified for a Japanese-market audience.

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 and a fully documented 4-parameter schema, the description supplies the missing behavioral pieces (units in yen, adjustment method, cost, range limits, timezone). Adequate for an agent to call correctly, though return structure (series length, gaps for non-trading days) is left implicit.

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. The description adds real meaning beyond the schema by clarifying that from/to are Japan-time dates and that weekly/monthly collapse the series to the last trading day of each period, but the interval semantics are largely restated from the schema.

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?

States a specific verb and resource ('Daily market capitalization of a Japanese stock') and even discloses the computation formula (split-adjusted close x shares outstanding, treasury excluded), which makes its output concept clearly distinct from a snapshot tool. It does not explicitly name the sibling it differs from (e.g. get_market_capitalization or get_valuation_history), so it stops short of a 5.

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?

Gives useful operational guidance: default is the last year, max 10 years per request, and interval=weekly/monthly thins the series. It never says when to prefer this over get_valuation_history or get_market_capitalization, and offers no exclusions, so usage context is implied rather than stated.

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