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

No annotations are provided, so the description carries the full burden. It discloses meaningful behavior beyond the basic function: the count is returned in the response rather than hardcoded, tickers appear only when resolved, FIIs are excluded, and no authentication key is needed. This is strong behavioral context for a zero-parameter tool.

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 main action and scope are front-loaded, and the exclusion note is efficient. The meta-explanation about why the count is not written in the description is slightly verbose, but it does serve a purpose for AI clients reading the description.

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 parameterless listing tool with no output schema, the description is complete: it covers scope, returned fields, response count behavior, exclusions, sibling alternatives, and access requirements. Nothing essential for correct invocation is missing.

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?

There are zero parameters, so the baseline is 4. The description adds useful output-field semantics (nome, CNPJ, ticker) but there are no parameters for it to document.

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 verb and resource: 'Lista as companhias abertas brasileiras (AÇÕES)', with the returned fields named (nome, CNPJ, ticker). It explicitly separates this tool from FII tools, so an agent can distinguish it from fiis_ranking and fii without opening schemas.

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?

Gives explicit when-to-use guidance: only stocks, and explicitly excludes real estate funds. It names the alternatives for FII use: fiis_ranking for the list and fii for a single fund. It also states access requirements upfront: 'Gratuito, sem chave'.

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