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

Annotations already cover the safety profile (readOnly, not destructive, closed-world), and the description adds real behavioral context on top: the shape of the returned summary, an update-frequency-independent "insufficient history" signal under 3 distinct days, and the fact that all text is Brazilian Portuguese. It does not mention rate limits or latency, but this is well beyond the annotation baseline.

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 compact sentences, front-loading the resource and purpose before listing outputs and edge-case behavior. Slight awkwardness in "Says so when..." (the agent as subject is unstated), but no sentence is wasted.

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 an output schema present, the description needn't enumerate return values, yet it summarizes them helpfully for selection; annotations cover safety and the schema covers the required param. The only real gap is that period's semantics (what each window means) are left to the enum alone.

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 50%: product_id is fully documented in the schema (including how to extract it from the URL), while period is undocumented beyond its enum and default. The enum values 30d/90d/1y are largely self-explanatory, but the description adds no meaning for the window or its default, 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 specific verb+resource ("Price history of a product") and the analytical intent ("to judge whether a discount is real"), which is unambiguous and distinct from reading a single current price. It stops short of naming how it differs from siblings like get_product or get_deal, so 4 rather than 5.

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?

"to judge whether a discount is real" implies the scenario the tool serves, and the caveat about needing 3+ distinct days effectively signals a limitation. However there is no explicit when-to-use-vs-alternative routing against get_product or get_deal, leaving usage to inference.

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