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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely useful non-annotation context: it consumes 1 credit per call and is available on all plans — relevant for quota-aware tool selection. However it says nothing about behavior on invalid or nonexistent CPFs, data freshness, or rate limits, which is the remaining behavioral gap.

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 payload description, then two short clauses for cost and plan availability; no filler or marketing language. The field enumeration is long but earns its place because no output schema exists. Slightly list-heavy, but every element carries information.

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 lookup with no output schema, the description compensates well by enumerating the returned fields and disclosing credit cost and plan coverage. The main omission is failure behavior (nonexistent/invalid CPF) and whether personal data returned has usage restrictions, which an agent might need before calling at scale.

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 description coverage is 100% and the single parameter 'cpf' is already documented as 11 digits with or without punctuation. The description only echoes the lookup key ('pelo CPF') and adds no format, validation, or normalization detail beyond the schema, so the baseline 3 applies.

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 resource and lookup key: registration data for a person by CPF, followed by an explicit enumeration of the returned fields (name, birth date, Receita Federal status, death indicator, phones, emails, addresses). That lets an agent distinguish it from the obvious sibling ficha_cnpj (company counterpart) without opening the schema. It stops short of naming overlapping siblings such as contatos_cpf, so sibling differentiation is only partial.

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 implies the tool requires a CPF ('pelo CPF') but never states when to pick it over buscar_pessoa_por_nome (search by name) or contatos_cpf (contacts only), nor any precondition such as having a valid or existing CPF. No when-not-to-use condition or alternative routing is given, so the agent must infer selection from tool names alone.

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