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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), yet the description still adds real value: the silent fallback to the prior rights date's short balance when shortageShares is omitted, the return shape (period total plus per-day equivalent in yen/share), and the rule that temporaryMultiplier is not multiplied with other multipliers.

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 short sentences, zero waste, with the core action front-loaded and the fallback and return format following in order of importance. Nothing is redundant or padded.

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 single-symbol, read-only prediction tool with an output schema and full schema coverage, the description supplies the essentials: what is predicted, the default input behavior, and the output units. Only a brief note on how it relates to the max-gyakuhibu calculator is missing.

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%, so all four parameters are already documented in the schema, including the same default behavior for shortageShares and the temporaryMultiplier rule. The description largely restates those schema descriptions rather than adding syntax, constraints, or edge-case meaning, so baseline 3 applies.

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 (予測する) and resource (次回の優待権利付き最終日の逆日歩, per share), plus the return units (円/株). It hints at the sibling calc_max_gyakuhibu via the '最高逆日歩計算機と同様' reference but never explicitly contrasts the two, so it stops short of full sibling differentiation.

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 by the purpose (predict the next rights date's charge) and the default-fallback rule for shortageShares is stated, but there is no explicit when-to-use / when-not-to-use guidance and no statement of how this differs from calc_max_gyakuhibu or estimate_cross_fee.

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