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

Annotations already declare readOnlyHint, openWorldHint=false, idempotentHint and destructiveHint=false, so the description's 'no side effects / deterministic' lines are largely redundant. However, it adds genuinely new operational context: the error-detection characteristics (all single errors and adjacent transpositions), the explicit 'validation only' framing, and concrete limits (64 KB input, 1 s per call, 1 MB result).

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-loaded with the purpose, then a tight When/Not-for/Side-effects/Deterministic/Limits structure that is easy to scan. Points deducted because the full ES and EN blocks are near-duplicates, and the trailing '[EN completo / full EN: inputSchema.description]' pointer is redundant filler.

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, read-only boolean validator with a rich annotation set and an output schema, nothing material is missing: it covers what is validated, what the input must contain, when to use it, the alternative, and execution limits. Return-value shape is correctly left to the output 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?

With 100% schema coverage, the schema already carries the pattern and examples, so the baseline is 3. The description earns one more by clarifying the semantics that the pattern cannot express: the final digit IS the check digit, i.e. the input must include it rather than the bare payload.

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 (valida/validates) and resource (a digit string with the Verhoeff dihedral-group checksum), and explicitly notes the last digit is the check digit. It also names the sibling it is not (damm) and gives a concrete real-world anchor (Aadhaar), so an agent can distinguish it from the dozens of other checksum validators without opening a 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 an explicit 'Cuándo/When' clause (verify an identifier's format and check digit offline before use) and an explicit 'No para/Not for' clause pointing to the damm sibling. Both the positive trigger and the exclusion are spelled out rather than inferable.

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