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

With no annotations, the description must carry transparency. It discloses determinism, citation of primary sources, and a billing policy ('errors and unverified rules are never billed'). This adds useful behavioral context, but it omits potential side effects like billing implications, required authentication, or how the tool handles edge cases. The 'cites primary sources' could imply quality assurance, but it's not a direct 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 description is a single sentence that packs multiple capabilities and policies. It is efficient and front-loaded with the main functions. However, it crams so much into one sentence that it feels rushed; a structured breakdown of modes would be clearer. Still, it earns a 4 because there is no fluff.

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?

Given 10 parameters, 1 required, no output schema, and no annotations, the description is far from complete. It does not explain the required 'mode' parameter, expected date formats, what 'kind' refers to, or how 'saturday_off' affects calculations. The tool appears complex (multiple functions), yet the description provides only a high-level teaser without operational details.

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 only 10% (only x_payment has a description). The description names high-level functions (e.g., 'business-day arithmetic', 'wareki conversion') but never maps them to specific parameters like mode, date, days, etc. It does not explain how parameters interact or what values are expected. This is a significant gap for a tool with 10 parameters.

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 lists the tool's capabilities: Japanese holidays, business-day arithmetic, statutory filing deadlines with holiday shift, and wareki conversion. It conveys a specific multi-purpose role and differentiates from sibling tools like jp_company_profile or jp_consumption_tax by focusing on dates and deadlines. However, it lacks a single verb+resource phrasing and doesn't explicitly state what the primary output is.

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?

No guidance on when to use this tool versus alternatives. The description lists functions but does not mention prerequisites, typical use cases, or any exclusions. It does not explain which mode to choose for what purpose, nor does it reference sibling tools for comparison.

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