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

Annotations already declare readOnly/idempotent/non-destructive, so the description's added value is the auth tiering (key required except BOVA11), the truncation behavior without a key (last 30 pregões, BOVA11 full), and the mode switch `serie=True` expanding to a daily series with adjusted close and reinvested-return columns. That is concrete behavior beyond the structured fields; it doesn't cover rate limits or error modes.

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-loaded with the payload summary, then the access rule, then the `serie`/date-range modifiers in a logical order. It is dense and field-heavy but nearly every clause carries information an agent needs; only the long parenthetical column list feels padded.

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?

No output schema exists, so enumerating returned sections (cadastro, informe diário, ágio/deságio, carteira, retornos) is doing necessary work, and the `serie` variant's columns are described. The missing pieces are date-input format and ticker conventions for a 5-param tool.

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?

With 0% schema description coverage the description must carry all five params, and it largely does: `serie` toggles the daily-series output, `de`/`ate` clip the range, `chave_api` gates non-BOVA11 access, and `ticker` is implied by the BOVA11 example. It omits date format for `de`/`ate` and ticker format, which keeps it from 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?

Opens with a specific verb+resource ('Detalhe de um ETF') and then enumerates the concrete payload: CVM/B3 registration, latest daily report, premium/discount over 30 sessions, fees, top-10 portfolio, overlap, returns. That is far more than a restatement of the title. It does not name a sibling (etfs_ranking, fii) to differentiate against, so it stops short of a 5.

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 real access guidance — BOVA11 is open for degustação, other tickers require chave_api (free or Pro), and without a key you get a 30-session sample. However it never says when to reach for this tool rather than etfs_ranking or fii, so alternative selection is left implicit.

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