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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, and the description goes well beyond them: it states no network access, no stored state, determinism, and concrete limits (64 KB input, 1 s per call, 1 MB result). The error-detection claim is genuinely useful behavioral context an agent cannot get from 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?

Content is well front-loaded and organized under labeled headings (Cuándo / No para / Efectos secundarios / Determinista / Límites). However, the entire block is duplicated verbatim in Spanish and English, roughly doubling length for an agent that only needs one rendering, which dilutes conciseness.

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 validation tool with full annotation coverage and an output schema, nothing is missing: scope, exclusions, limits, determinism, and side effects are all stated. The description does not need to explain return values because an output schema exists.

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 the parameter already documents the pattern and that the check digit is included, so the baseline is 3. The description reinforces the critical semantic point — that the last digit is the check digit and validation is all-or-nothing — which slightly reduces the risk of an agent passing a body without its check digit.

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?

States a specific verb and resource ("Valida un número con el dígito de control Damm") and adds the algorithm's discriminating property (detects all single-digit errors and adjacent transpositions). It explicitly separates itself from the sibling checksum tool by name (verhoeff), so an agent can route correctly without opening either 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?

Provides explicit labeled guidance: "Cuándo: hay que verificar sin conexión..." gives the use condition, and "No para: validar un número con el dígito de control Verhoeff (verhoeff)" gives the exclusion plus the exact alternative tool. This is the when/when-not/alternative triad in full.

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