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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds genuinely useful behavior beyond them: each section carries `dados_ate` per source because source lag differs, so stale sources are visible rather than masked, plus 'gratuito, sem chave'. This freshness semantics is real added value; only the return shape stays underspecified.

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-loads the core scope in the first sentence and then layers detail in a controlled way; every clause maps to a concrete output section. It is somewhat verbose with illustrative parentheticals, but nothing is padding and the key constraint (fixed 30-day window) sits early.

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 input params, rich read-only annotations, and no output schema, the description does the needed work: it enumerates the returned sections and explains the per-source freshness field. It is close to complete for a zero-arg aggregator, though it could more explicitly route agents away from the overlapping sibling tools.

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 tool takes zero parameters, so the schema carries nothing to misinterpret and the baseline of 4 applies. There is no parameter meaning for the description to add or omit.

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 scope ('o que mudou no mercado brasileiro nos últimos 30 dias') and enumerates the covered content (balanços, documentos reenviados, proventos, eventos societários, trocas de ticker), so the agent knows exactly what the resource is. It implicitly differentiates from annual-series tools ('a pergunta que nenhuma série anual responde') but never names the overlapping siblings like eventos, reapresentacoes, or dividendos, so sibling disambiguation is incomplete.

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?

Frames the use case via the question it answers ('o que aconteceu com a empresa X esta semana'), which implies when to reach for it. However, there is no explicit when-not guidance and no named alternative when a narrower tool (eventos, reapresentacoes) would be preferable, leaving routing to inference.

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