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

Annotations already cover readOnly/idempotent/non-destructive, and the description goes well beyond them: per-address rate limits (1000/h, 10000/day), key-based limit substitution, unauthenticated sampling limited to the last 30 pregões with MXRF11 as the full-data exception, and unadjusted series with flagged jumps. It stops short of explaining what 'citacao' actually is or the shape of the paid serie output, which keeps it from a 5.

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 core capability is front-loaded, which is good, but the text is a dense run-on with nested parentheses and awkward line wrapping that mixes return contents, auth rates, and sampling policy in one block. The rate-limit clause is useful yet could be stated once more crisply.

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 5-parameter read tool with no output schema, the description is nearly sufficient: it names what comes back, what `citacao` accompanies results, and how behaviour degrades without a key. The only real hole is the unexplained `de`/`ate` window on the historical series.

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 carries the full burden. It adequately explains `serie=True` (daily columns, no adjustment, jumps signalled) and `chave_api` (limit behaviour), but `de` and `ate` are never mentioned and must be guessed as the serie date window. Ticker and the default sample/full distinction are only implied.

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 states a specific verb and resource ('Detalhe de um fundo imobiliário') and enumerates exactly what is returned (cadastro, último informe, série P/VP, DY 12m, rendimentos). The 'ABERTA: qualquer FII, sem chave' framing implicitly differentiates it from the ETF/BDR siblings, though it never names fiis_ranking or screener_fiis to sharpen the boundary.

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?

'um por vez' and the open-access/rate-limit note give some usage context, but there is no explicit statement of when to prefer this over fiis_ranking, screener_fiis, or dividendos. The agent must infer that this is the single-ticker drill-down and the others are list/rank tools.

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