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

Annotations already declare readOnly, idempotent, non-destructive behavior, so the description's job is smaller, and it still adds real value: the per-call request cost, the fact that WhatsApp data appears only when available, and the explicit bounding of the payload to contacts. It does not describe error behavior for an unknown or malformed CPF.

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 clauses, zero filler, with the scope constraint front-loaded before the cost note. Every sentence carries distinct information an agent needs.

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 no output schema, the description usefully enumerates the returned payload (phones, WhatsApp presence, e-mails), so an agent knows what comes back without a second call. Minor gap: no mention of what happens when the CPF has no registered contacts.

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 cpf parameter is already documented as 11 digits with or without punctuation, so the description adds no format or validation detail beyond the schema. Baseline 3 applies because the schema carries the parameter semantics.

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 precise verb-and-resource: returns only phones (with WhatsApp flag when present) and e-mails for a given CPF. The clause 'sem o restante da ficha' explicitly separates it from the full-profile sibling ficha_cpf, so an agent can route without opening either 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?

'Só os contatos... sem o restante da ficha' gives a clear selection condition against the fuller profile tool, and the cost note ('Consome 1 requisição') helps when the agent is deciding whether a lightweight lookup suffices. The alternative is implied rather than named outright, so there is no explicit 'use X instead' instruction.

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