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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond that: it names actual source kinds (FR/UK/HK government feeds, OpenHolidays entries) and warns that international coverage is incomplete. Missing caveats about how freshness is computed or how often the catalog changes keep it from a 5.

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?

Four short sentences, front-loaded with what is discoverable before routing advice and caveats. Every sentence carries distinct information; nothing repeats the annotations or schema.

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 documentation is not needed. With zero parameters and complete annotations, the description supplies the missing pieces: what the catalog contains (region ids, years, source kind, freshness), when to choose it over get_public_holidays, and two important coverage limitations.

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?

The tool takes zero parameters, so there is no parameter syntax to explain; baseline for a zero-parameter tool is 4. The schema is trivially fully covered, and the description correctly spends no space re-documenting inputs.

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 and resource ('Discover available public-holiday calendars') and enumerates exactly what the response provides: exact region ids, published years, source kind and freshness. It explicitly names the sibling it is not, get_public_holidays, so an agent can route between them without opening schemas.

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 an explicit conditional: use this when country/region/year coverage is unknown, otherwise call get_public_holidays directly. It also adds the crucial caveat that configured calendars are not proof of available data, which prevents a false inference about coverage.

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