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

Annotations already cover the safety profile (readOnly, idempotent, closed-world), and on top of that the description explains what the data actually means: 'verified' is proven by a time-weighted median of our readings and can be quoted as savings, 'none' means no assertable discount, and the seller's 'de' price is explicitly not evidence. That is substantive behavior beyond the structured fields.

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 purpose is front-loaded, but the 'de' price warning is stated three times ('o "de" do vendedor não conta', 'O preço "de"... não sustenta desconto nenhum aqui', plus the certainty rule), which is emphasis at the cost of 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?

With no output schema, the description carries the burden of explaining returns and does so for the critical field (discount.certainty). It does not describe the rest of a product's shape (title, price, link), but nothing needed to call it correctly is missing.

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 83%, including the important caveats on busca, categoria and apenas_verificados, so the schema does the heavy lifting. The description adds no parameter-level detail of its own, so the 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 a specific verb and resource ('Lista produtos da Shopee Brasil com queda de preço real'), plus the mechanism behind it (30-day history). It does not, however, distinguish itself from the siblings quedas_de_preco or historico_de_preco, so an agent cannot tell from the text alone which of the three to pick.

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?

There is real usage guidance about how to present results ('Citar o percentual sem o certainty ao lado desinforma o leitor') and a scoping caveat inside the busca param (not a full-catalog search). But there is no explicit when-to-use/when-not versus the price-drop and price-history siblings, so selection guidance is only implied.

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