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

Annotations already cover the read-only, idempotent, closed-world profile, so the bar is lower. The description still adds real behavior beyond them: it accepts either an itemId or a full URL, it returns a reading count alongside the series, and the response explicitly flags the under-three-readings case as insufficient evidence for a decline — a non-obvious output contract.

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?

Three short sentences, front-loaded with what the tool returns, then the input forms, then the caveat. Nothing is repeated and nothing is padding.

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 one-parameter read-only tool with no output schema, the description covers input forms, the returned series, and the reading-count caveat. The remaining gap is interpretive: it never states the period or granularity the series spans, which matters for judging a price trend.

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 100% and the single parameter already documents both accepted forms (numeric itemId or full product URL) with an example format. The description restates exactly that, adding no syntax, validation, or edge-case detail beyond the schema, 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 a concrete resource — the observed price series for a Shopee product — plus the accepted identifier forms and the extra reading-count field. It never names quedas_de_preco or buscar_promocoes, so the boundary between 'give me the raw series' and 'give me detected drops' must be inferred from the wording.

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?

Usage is only implied: the note that fewer than three readings cannot support a drop claim hints at when this raw-series tool is the right primitive, but the description never says when to call it instead of the sibling quedas_de_preco (which presumably already applies that rule). No exclusions or prerequisites are stated.

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