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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the 'sin efectos secundarios' sentence largely repeats structured data. The description still earns credit for details the annotations do not carry: determinism, the 64 KB input cap, 1 s per call, and 1 MB result limit.

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, when, not-for, side effects, determinism and limits are all front-loaded before the limits section. The Spanish and English blocks are near-complete duplicates, which is defensible for a bilingual server but roughly doubles the length for the same information.

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?

With an output schema present, return-value explanation is unnecessary, and the description covers purpose, routing, determinism and resource limits. The only loose end is the 'optionally increased or decreased' wording, which is not reconciled with the actual two-parameter schema.

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% and both parameters (percent, value) are documented in the schema with examples, so the baseline is 3. The description adds no format or boundary detail beyond what the schema states, and its phrase 'optionally the value increased or decreased by p%' implies an option the two-parameter schema does not expose.

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 opens with a specific verb and resource ('Calcula el p% de un valor' / 'Computes p% of a value'), and explicitly distinguishes the tool from its sibling percent-change. An agent can tell what it produces without reading the schema.

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?

It gives an explicit 'When' condition (exact/reproducible numeric result rather than an estimate) and an explicit 'Not for' that names the alternative tool (percent-change) and the case it covers. This is the full when/when-not/alternative pattern.

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