期限からの逆算日を計算

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

Annotations declare readOnlyHint=true and openWorldHint=false, so the read-only nature is already known. The description adds valuable context beyond this: it explains that weekends and holidays are not counted ('土日・祝日は数えず') and that the calculation is based on actual business days for action, which provides deeper behavioral transparency without contradicting the 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?

The description is only two sentences, with the core action and output stated first, followed by a practical use case and the business-day behavior. Every sentence earns its place with no ifs, buts, or unnecessary filler.

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 simple calculator with two parameters and no output schema, the description is quite complete: it explains the purpose, the use case, and the holiday-excluding behavior. The only minor gap is that it does not explicitly state the output format (e.g., YYYY-MM-DD), but given the tool's simplicity and the schema's date pattern, this is not a significant omission.

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?

The schema covers both parameters with 100% description coverage, including formats and constraints. The description reinforces their meaning by specifying that businessDaysBefore is a count of business days before the referenceDate (e.g., '指定した営業日数だけ前'), and it gives an example usage. This adds a bit beyond the baseline for full schema coverage.

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 clearly states what the tool does: it calculates the 'action deadline date' that is a specified number of business days before a reference date. It uses a specific verb ('計算します') and resource ('基準日から...逆算'), and it distinguishes itself from sibling tools by emphasizing the backward counting direction, unlike add_business_days.

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 provides a concrete use case: '「基準日のX営業日前までに提出・対応する」という管理(更新期限のリマインダー設定など)に使えます。' This clearly indicates when to use the tool. However, it does not explicitly mention when not to use it or contrast with sibling tools, so it lacks the explicit exclusion criteria for a 5.

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