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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is covered. The description adds the key behavioral rule: unchanged when already a business day, shifted by direction otherwise, plus the default-to-next behavior. It doesn't state the return format (a date string) or what happens at range boundaries.

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?

Two parallel sentences (EN/JA) that are front-loaded with the core rule and free of filler. The bilingual duplication roughly doubles length but is a deliberate convention here, not padding.

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-value transform with a fully documented 5-parameter schema, this covers the decision logic and the intended use case. Gaps are minor: no statement of the returned value type or behavior when no business day is found within the extra-* constraints.

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% and the enum parameters (calendar, direction) are already fully documented in the schema, including the bank-holiday distinction. The description only restates 'next'/'previous' semantics, adding little beyond the schema baseline.

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+resource ('adjust a date to a business day') and spells out the two directional behaviors. It is distinguishable from add_business_days (offset) and check_business_day (predicate), though it never names those siblings explicitly.

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 a concrete use context ('payment due dates that fall on holidays') and implicitly defines the scenario via the business-day/non-business-day branch. It stops short of explicitly excluding or routing to sibling tools.

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