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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so safety is covered. The description still adds value with determinism and concrete operational limits (64 KB JSON input, 1 s per call, 1 MB result), though determinism largely restates idempotentHint.

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?

Front-loads purpose, then when/not-for, side effects, determinism and limits in a scannable order. The full Spanish+English duplication doubles length, but the repetition is intentional for bilingual coverage rather than padding.

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 single-parameter math tool with an output schema, the description covers what it returns (lowest terms, mixed, decimal), when to use it, the alternative, and operational limits. Nothing needed 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?

Schema coverage is 100%, so the baseline is met by the schema. The description goes further by enumerating accepted input formats — "6/8", "-10/4", "1 1/2" mixed, "0.375" decimal — which tells the agent what to pass beyond the single schema example.

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?

Starts with a specific verb and resource ("Simplifica una fracción a su mínima expresión") and names the output forms (mixed, decimal) plus accepted input shapes. An agent can distinguish it from fraction-arithmetic and decimal-to-fraction from the text alone.

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?

Has explicit "Cuándo" (exact/reproducible numeric result, not estimated) and "No para" sections that name the alternative sibling fraction-arithmetic for add/subtract/multiply/divide. Routing is unambiguous.

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