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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, and the description adds real context beyond them: dates are cross-verified against an official government list and a second calendar, state/region applicability is included, and unconfirmed lunar holidays are marked. It doesn't discuss result size or paging, but the verification and confidence-marking behavior is the substantive disclosure an agent needs.

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, front-loaded with the use case, then return behavior, then exclusions — a sensible ordering with no filler. The opening sentence is long and carries the country list plus two example queries, which is dense but each element earns its place.

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?

There is no output schema, so the description carries the return-shape burden and does: dates, region/state applicability, and a confirmed-vs-expected distinction. Combined with annotations and a fully documented schema, an agent has everything needed to call this correctly and to know its limits.

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 baseline is 3, but the description adds a capability the schema lacks: the enumerated list of ten supported countries, which matters because `country` has no enum and would otherwise be unbounded. The date-range semantics of from/to are only implied ('next month'), which is why this is not a 5.

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 (return public holidays / observance days) and names the exact user intents it serves ('when is Hari Raya this year', 'holidays in Malaysia next month'). Nothing among the sibling tools (posting, insights, accounts, audio) overlaps, so an agent can route cleanly.

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 explicit triggers ('planning posts, promotions or opening hours') plus concrete example queries, and then explicit exclusions: not for other countries, not for school terms, and not to invent dates. Both the when and the when-not are stated.

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