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

With no annotations provided, the description carries the behavioral disclosure burden. It is transparent about the tool's scope, mentions the cost 'Cuesta UTIL', and explicitly warns that it does not confirm account existence. This goes well beyond a bare functional statement, though it could also disclose return behavior or errors.

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?

Three short sentences deliver the core purpose, a cost caveat, and a key limitation with no filler. The most important information is front-loaded and every sentence earns its place.

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?

The tool is simple with one parameter and no output schema, and the description covers its scope, cost, and limitation. The only notable gap is that it does not describe the result format or how an agent should interpret the validation outcome.

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?

The input schema gives no description for 'clabe', so the description must compensate. It does so by explaining the validation criteria and implicitly clarifying that the parameter is the CLABE number to be validated. It adds meaning beyond the schema, though it could explicitly specify the required string format.

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 clearly states the verb 'Valida' and the specific resource 'estructura de una CLABE' with concrete validation criteria: 18 digits, check digit, and bank by prefix. This distinguishes it from sibling validators like validar_curp or validar_rfc without needing to inspect 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?

No guidance is provided about when to choose this tool over alternatives or when not to use it. The caveat 'No confirma que la cuenta exista' is useful but does not name any alternative validation or verification tool for checking account existence.

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