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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety needs no restating. The description adds genuinely new behavior: the ~200-country coverage, the default exclusion of bank-only holidays, and the fact that results flag which holidays are nationwide versus regional.

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 action, then a compact 'Use when:' line, then one example call — no filler sentences. The density is high but every clause (country coverage, return fields, bank-holiday exclusion) carries information.

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?

Three flat parameters, all documented, and the description tells the agent what the response contains (dates, dual-language names, geographic scope). With annotations covering the safety profile and no output schema gap remaining, an agent has everything needed to call this correctly.

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% and all three parameters are already documented with defaults and a country example, so the baseline is 3. The description's worked example {"country":"DE","year":2027} and the 'unless asked' clause reinforce the include_bank_holidays default but add no syntax or format detail the schema lacks.

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?

Specific verb and resource ('Lists the official public holidays of a country for a year') plus scope detail (about 200 countries) and the returned fields (date, English and local name, nationwide or regional). The year-scoped list framing separates it in spirit from 'is_public_holiday' and 'next_public_holidays', but no sibling is named, so the differentiation is implicit rather than explicit.

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?

A dedicated 'Use when:' line with concrete example queries in two languages and a real use case (planning deliveries or meetings) gives a clear trigger context. It stops short of exclusions — nothing says to use next_public_holidays for upcoming-only requests or is_public_holiday for single-date checks.

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