validar_cpf

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

With no annotations provided, the description fully covers behavioral traits: it is a mathematical verification, done offline without external calls, and notes the limitation of missing public API for CPF data. This is comprehensive for a validation tool with no side effects.

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?

The description is extremely concise with two sentences: the first states the purpose, the second adds context. There is no extraneous information, and every sentence is necessary and front-loaded.

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?

Given the simplicity of the tool (1 parameter, no enums, output schema exists), the description fully covers what the agent needs to know: what it does, how it works (offline), and limitations. The output schema handles return values, so no further explanation is needed.

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 already describes the parameter format. The description adds value by clarifying that the tool validates the check digit and that the operation is offline, providing context beyond the schema. This raises the score above the baseline of 3.

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 uses specific verbs ('Valida o dígito verificador') and resource ('CPF brasileiro'), and clearly distinguishes itself from sibling tools by emphasizing offline mathematical verification without external API consultation. Among siblings, there is no other CPF validation tool, so it stands out.

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?

The description explains that it performs offline mathematical verification and notes that the Receita Federal does not provide public CPF data APIs, implying when to use (format/check digit validation) and warning against expecting API-based data. However, it does not explicitly mention alternatives like consultar_cnpj for full CPF data, which could be clearer.

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