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

With no annotations provided, the description carries the full burden and does meaningful work: it discloses the dataset is 'Free' (no auth/key implied), reveals that both national and banking holidays are mixed in via a 'kind' field, and supplies a concrete example response. It stops short of describing error behavior or what happens for out-of-range years, so it is strong but not exhaustive.

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?

Purpose and scope are front-loaded in the first clause, followed by a short inclusion list, a one-word cost note, and an example. Nothing is padded, although the embedded example makes the single 'sentence' long.

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?

For a one-parameter read tool with no annotations and no output schema, the definition covers what is needed: what data comes back, the shape of the response (via example), and cost. The main omission is boundary/error behavior for the year range, which is a minor gap given the tool's simplicity.

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?

One parameter at 0% schema coverage, so the description must compensate. The phrase 'for a year' plus the example {"year":2026} makes the parameter's meaning and expected format clear, but the description never states the accepted range (1990–2100 lives only in the schema) or what an invalid year returns.

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 states a specific resource and scope: Brazilian national and banking holidays for a given year, and even enumerates notable entries (Carnival, Good Friday, Corpus Christi, Nov 20). It is immediately clear what the tool returns, though it never explicitly contrasts itself with the sibling 'business_days', which is the most likely confusion point.

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?

There is no when-to-use guidance, no prerequisites, and no named alternative. A reasonable agent can infer this is for fetching holiday calendars, but nothing tells it when to prefer this over 'business_days' or how the two differ (holidays vs. computed working days).

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