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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is carried. The description adds useful scope context (200+ countries, subdivision-level detail) that tells the agent what data granularity it will get, though it says nothing about rate limits, auth, or ordering of results.

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 sentences, each earning its place: usage triggers first, capability scope second, exclusion/alternative last. No filler, no repetition of the tool name, and the routing guidance is front-loaded.

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-value explanation is unnecessary, and annotations cover the safety profile. With a 3-param schema at full coverage plus explicit when/when-not guidance, nothing an agent needs to select or invoke this tool correctly is missing.

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 all three parameters (country ISO code, year range, region ISO 3166-2 with the 'supply it or only nationwide holidays are returned' warning) are already fully documented. The description only restates the country/region/year dimensions without adding syntax or format detail, so the 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?

States a specific verb+resource (list public holidays) and immediately bounds it by country/region and year, plus coverage breadth (200+ countries, state/province detail). It also names the sibling it is not (add_business_days), so an agent can separate it from the three related tools without opening any schema.

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 three concrete trigger conditions (what holidays exist in a country/region, when a specific holiday falls, how many holidays a year has) and an explicit exclusion with a named alternative: 'Do not use it for working-day arithmetic; use add_business_days for that.'

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