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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuinely new context: the coverage footprint (100+ countries, states/regions, any year), localized naming, and the upstream data source with license. It omits return shape and rate/limit behavior, but for a read-only lookup this is solid.

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?

"Public holidays of a country. Holidays of a year." is largely a restatement of the title and wastes the front position. The third sentence is dense and useful, and the data-source line is a quiet but legitimate attribution, so the result is adequate rather than tight.

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?

Read-only annotations plus a fully described 5-parameter schema and no output schema mean the description need not carry much. The gap is the advertised 'is this date a holiday?' check: no date parameter exists in the schema, so an agent following that claim has no way to invoke it and no explanation of where the check lives.

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%, so the schema already documents lang, year, state, types and country. The description lightly echoes these concepts (localized names, any year, states/regions, public and bank holidays) but adds no syntax or format detail beyond the schema's own examples, 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 concrete resource and scope: public and bank holidays for 100+ countries and their states/regions, any year. However, it claims to include an "'is this date a holiday?' check" that overlaps with the dedicated sibling is_public_holiday without routing the agent, so the boundary between the two tools is blurred rather than clarified.

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?

No when-to-use guidance and no explicit alternative is named, even though is_public_holiday in the sibling list is the obvious competing choice for single-date checks. The description actually muddies this by advertising the same check here, so the agent gets no tie-breaker.

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