etf

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

With no annotations provided, the description carries the behavioral disclosure burden. It actively explains the analytical nuance that return by COTA is total return by construction (ETF reinvests) and that screen price can diverge from cotação, with ágio quantifying that divergence. It also discloses the API-key requirement through the 'BOVA11 é aberto como degustação' note. These go beyond the basic 'what it does' and provide meaningful behavioral context.

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 moderately long but every segment is purposeful: a comprehensive data list, an explanatory note on return types, and parameter definitions. It is front-loaded with the tool's scope and the analytical caveat is placed logically. While a bit dense, it does not contain filler and earns its length.

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?

Given no output schema, the description does a strong job of enumerating what the agent will receive: cadastro, informe diário, ágio/deságio, taxa efetiva, carteira, sobreposição, and returns. Together with parameter semantics and access note, an agent has enough to call the tool correctly. It does not specify exact return formatting or error behavior, but the data scope is well covered.

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 schema provides no descriptions (0% coverage), but the description fully compensates: it defines ticker as 'código do fundo na B3' with examples (BOVA11, IVVB11), and chave_api as 'chave do Dados B3', including the access context of BOVA11 being open for trial. Both parameters are semantically enriched beyond the raw schema.

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 clearly identifies the resource (a single B3 ETF) and enumerates its contents: registration, daily report, agio/disagio, effective rate, portfolio, overlap, and returns. This distinguishes it from siblings like etfs_ranking (which implies ranking of multiple ETFs). It lacks an explicit action verb like 'returns' or 'fetches', but the list of data categories makes the purpose unambiguous.

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?

The description implies usage for single-ETF data retrieval and notes that BOVA11 is available as a free sample, providing context on when to use it. However, it does not explicitly contrast it with sibling tools such as etfs_ranking or screener, nor state when not to use it. The usage context is clear but relies on inference.

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