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

Annotations already cover readOnly, non-open-world, idempotent and non-destructive, yet the description still adds genuinely new context: no network, no stored state, determinism, and concrete limits (64 KB input, 1 s per call, 1 MB output). The determinism sentence largely restates idempotentHint, which is why this is a 4 rather than 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?

Purpose is front-loaded and the when/not-for/side-effects/limits ordering is easy to scan. However, the description block contains a partial English restatement that duplicates the Spanish text already present, adding avoidable length.

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 computed tool with an output schema and full annotations, the description covers scope, exclusions, side effects, determinism and operational limits. Nothing an agent needs in order to call it 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?

There is a single parameter with 100% schema description coverage, including min 1583, max 4099 and an example, so the schema already carries the semantics. The description restates the year range but adds no new meaning such as behavior at boundaries, which fits the baseline 3.

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?

Names the specific resource and computation ('Domingo de Pascua occidental y ortodoxo') plus the related dates it returns, so the agent knows exactly what is produced. It also explicitly rules out the closest sibling case (Colombian national holidays with Ley Emiliani), which is the one an agent could plausibly confuse it with.

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?

Provides an explicit 'Cuándo' trigger (exact date/calendar results) and an explicit 'No para' exclusion naming the sibling domain co-holidays. The when/when-not/alternative structure is fully present, leaving nothing to inference.

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