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

Annotations already cover safety (readOnly, idempotent, non-destructive), and the description adds genuinely new context: no API key required, one ticker per call, concrete rate limits (1000/hour, 10000/day per address) that change when `chave_api` is supplied, and the presence of a ready-to-use `citacao` field.

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?

Content is front-loaded and every line carries information (scope, exclusions, limits, return value). The dense telegraphic fragments ('ABERTA:', 'Só ações.') and hard line breaks make it slightly harder to parse than a cleanly structured 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 2-parameter read-only lookup with no output schema, the description covers scope, exclusions, auth, limits and the headline return field. Minor gaps remain: it doesn't say what an invalid/unknown ticker yields or the exact shape of the quality flags, though the `citacao` promise partly compensates.

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 coverage is 0%, so the description must carry the load and largely does: it explains `ticker` (a B3 stock symbol, explicitly excluding FIIs ending in 11) and `chave_api` (optional key that raises rate limits). It does not state format expectations such as case or the '.SA' suffix convention, which would have earned a 5.

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 (annual series 2010–today) and enumerates the exact metrics returned (ROIC, ROE, margins, growth, net debt/EBITDA) plus quality flags. It also scopes it to B3 stocks, distinguishing it from `fii` and the quarterly `trimestres` tool.

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?

Explicitly names when NOT to use it: FII tickers ending in 11 (e.g. MXRF11) must go to `fii`, with the reason given (no ROIC/EBITDA for FIIs). It also pre-empts a common edge case by noting banks/insurers are accepted but return no ROIC/EBITDA.

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