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

Annotations only mark non-read-only and non-destructive; the description adds that the call is covered by package balance, implying a balance-consuming operation, and clarifies the scope with the affiliation disclaimer. The balance wording is slightly ambiguous but there is no contradiction with 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?

Two short sentences, front-loaded with the core action and validation type, followed by billing and exclusion notes. Every sentence earns its place with no fluff.

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 one-parameter validation tool with output schema present and annotations covering safety, the description covers purpose, scope, and billing context. It lacks an explicit alternative for affiliation confirmation, but that gap is minor given the tool's simplicity.

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 0% schema coverage for the single 'nss' parameter, the description compensates by defining NSS as a social security number and indicating that format and Luhn digit are validated, giving the agent enough semantic grounding to populate the parameter with a user-provided NSS.

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'), a specific resource (NSS), and the exact validation criteria (formato y digito Luhn). The explicit disclaimer that it does not confirm IMSS affiliation prevents confusion with larger verification tools among the siblings.

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?

Gives a clear exclusion: this tool does not confirm affiliation with IMSS, so agents know not to use it for that purpose. It also notes the package-balance inclusion. However, it stops short of naming an alternative sibling (e.g., verificacion_completa) for affiliation checks.

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