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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuine context beyond that: which report sources feed the data (Shopee Canal/Referenciador, Magalu origin) and the important caveat that marketplaces without this dimension are silently excluded — a completeness limit an agent must know before presenting results as total.

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?

Two sentences, front-loaded with the dimension and metrics, followed by the source/caveat sentence. Dense and efficient; only the parenthetical channel examples could be trimmed.

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?

With no output schema, the description usefully enumerates the returned metrics and the data provenance, and the schema covers the time-window parameters. Remaining gaps are modest: no mention of totals rows, channel-name normalization, or ordering of results.

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 description coverage is 100% and the three period parameters are fully documented there, including the days-vs-start/end relationship. The description adds no parameter guidance and does not restate the default window, so baseline 3 applies.

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 the resource precisely as a funnel broken down by acquisition channel and enumerates the returned metrics (cliques, pedidos, conversão, vendas, comissão, EPC). The capitalized 'CANAL' plus the explicit data sources clearly separate it from the other breakdown siblings, though no sibling is named directly.

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 when the tool is the right choice (you want performance per disclosure channel) and adds a real scoping rule — marketplaces lacking that dimension are absent from the result. It never explicitly contrasts with painel_get_subid_breakdown, painel_get_advertiser_breakdown or painel_get_top_links, so the agent must infer the boundary.

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