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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds critical context beyond them: AAPL34 is open while all others require `chave_api` (auth gating), what each mode returns, what is deliberately absent (código da ação lá fora, proporção BDR:ação), and an explicit non-recommendation disclaimer.

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?

Dense but front-loaded: the ticker="" list behavior is stated before the detail mode, and backticked parameter names plus uppercase emphasis make it scannable. Slightly long with parenthetical asides, but nearly every clause carries distinct information.

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, and the description compensates well by enumerating the returned fields for both modes and stating the auth gate. The main gap is the unexplained `de`/`ate` date-range parameters, which an agent cannot infer.

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 the load, and it explains ticker (empty vs set), tipo (filter), serie (daily closing sample of 30 pregões), and chave_api (auth requirement) richly. It omits any explanation of `de` and `ate`, leaving two of six parameters undocumented.

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 (BDRs negociados na B3), defines what a BDR is with concrete examples (AAPL34, NVDC34, IVVB39), and clearly distinguishes the two operating modes (`ticker=""` list vs `ticker` detail). An agent can tell this apart from siblings like etf, fii, or precos without opening the schema.

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 strong mode-selection guidance: empty ticker lists, `tipo=` filters, set ticker returns detail, `serie=True` returns daily series. However, it never explicitly contrasts this tool against sibling alternatives (etf, precos, dividendos) for overlapping needs, so it stops short of full when/when-not routing.

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