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

With no annotations, the description carries full disclosure responsibility and does so well: it reveals data-lag behavior (`dados_ate` per section, fixed window from today, stopped sources look stopped) and access constraints ('Gratuito, sem chave'). This is meaningful behavioral context beyond a simple 'returns data' statement.

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 front-loaded with the primary promise, then details the window contents, then explains the freshness semantics, then gives access info. Each sentence adds a distinct piece of information and none restates the title or schema.

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 no-parameter, no-output-schema tool, the description explains the relevant output categories and the `dados_ate` field meaning, which is sufficient for an agent to present results accurately. It still leaves minor ambiguity about how the 'empresa X' phrasing maps to an invocation with no parameters.

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 has zero parameters, so the description cannot add parameter-level detail; the 0-parameter baseline of 4 applies. The only relevant semantic detail, that no API key is needed, is stated in the description.

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 opens with a clear deliverable ('O que mudou no mercado brasileiro nos últimos 30 dias') and enumerates the concrete content: public filings, re-submitted documents, dividends, FII reports, corporate events, and ticker changes. It does not name sibling tools, and the 'empresa X' phrase is framed as a user question rather than an explicit scope, so it stops short of full sibling differentiation.

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?

It gives a clear context — use for recent changes that 'nenhuma série anual responde' and explicitly frames the 30-day window as the differentiator. It never names alternatives or says when not to use the sibling tools, but the context is specific enough to route an agent.

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