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

Annotations already declare readOnlyHint and idempotentHint, covering safety. The description adds valuable context about the 'puente' (nearest Monday) rule, clarifying that the dates returned are fixed legal calendar dates, not actual observance dates. This non-obvious behavior is critical to prevent misinterpretation and goes beyond the annotations.

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?

The description is three sentences with no wasteful words: purpose, usage scenarios, output format, and a caveat. It is well-structured, front-loaded with the primary action, and every sentence 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?

For a simple read-only tool with one parameter, the description covers purpose, usage, output format (dates in YYYY-MM-DD, names in Spanish and English), and a behavioral nuance. Since there is no output schema, a slightly more explicit return structure (e.g., array of objects) could elevate completeness, but it remains sufficiently informative.

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 schema fully describes the single 'year' parameter with type and example, so the description adds minimal extra meaning. It merely mentions 'any given year' and the output format, which aligns with the baseline score of 3 for high schema coverage.

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 begins with a clear action verb ('Returns') and specifies the resource as 'Mexican national public holidays' for any given year. This thoroughly distinguishes it from sibling tools for other countries (Argentina, Brazil, Chile) and validation tools, leaving no ambiguity about what the tool does.

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?

The description explicitly states when to use the tool: for calculating delivery dates, scheduling appointments, or any task requiring knowledge of non-working days in Mexico. It does not explicitly mention when not to use it or alternatives, but the sibling context and the country-specific scope make the boundaries clear.

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