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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the description correctly uses its space for what annotations cannot express: no network access, no stored state, determinism, and concrete limits (64 KB input, 1 s per call, 1 MB result). Only minor overlap with the read-only claim keeps it from a 5.

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 core purpose, then cleanly sectioned via labeled markers (Cuándo, No para, Efectos secundarios, Límites). The added 'EN:' line restates content already present in the inputSchema description, which is mild redundancy rather than waste.

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 one required parameter, full annotation coverage, an output schema, and no nesting, the description covers everything needed: input forms accepted, unsupported cases, side effects, determinism, and operational limits. Nothing an agent needs before calling 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% with a single documented 'id' parameter, so the baseline is 3. The description goes further by explaining what the input actually means — cédula form versus natural-person RUC with establishment suffix — which tells the agent what will and will not validate even though dashes are permitted.

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+resource ('Valida una cédula ecuatoriana... o un RUC de persona natural') with the exact validation rules (province 01-24, third digit 0-5, mod-10 coefficients, establishment 001-999) and explicitly rules out company/public RUCs. An agent can distinguish this from br-cpf-validate or mx-curp-validate without opening any 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' trigger (checking a user-supplied LatAm/Spanish ID offline before storing or using it) and an explicit 'No para' exclusion naming the sibling pe-ruc-validate. Both when-to-use and when-not-to-use are stated, not inferred.

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