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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower; the description still adds the 400-day range limit and, importantly, the error-on-missing-data behavior that an agent must not misreport. This is genuine beyond-annotation context.

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 compact sentences with no filler, and the scope (three holiday kinds, one country, up to 400 days) is front-loaded before the error caveat. Slightly dense but every clause 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?

An output schema exists, so return-shape explanation is not needed. With annotations covering safety and the schema covering all five parameters at 100% coverage, the description supplies exactly the missing pieces: scope, the range limit, and the error-interpretation caveat.

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 the schema already explains from/to defaults, the 400-day cap, the kind enum, and locale. The description adds only the note that school holidays are often regional with ISO 3166-2 codes and that traffic days are France-only, which mostly duplicates the schema's kind description. 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?

The description names a specific resource set — public holidays, school holidays, and official peak traffic days — scoped to one country over a bounded period, which is unambiguous. It lacks an explicit verb framing and does not name a sibling, but no sibling tool covers holidays, so confusion risk is low.

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?

It states the use cases directly ("Use it for public holidays, days off, school holidays and peak traffic days") and gives an operational rule about error results — "never present that as 'no holidays'". It does not name a when-not case or a competing tool, but the guidance is concrete and actionable.

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