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

Beyond the readOnly/destructive annotations, the description discloses concrete behavioral traits: a 95-calendar-day cap with explicit window-splitting arithmetic, ratio-recomputation warnings (ACOS/ROAS), interval-specific keyword-ranking limits (DAILY 90, RAW 31), the requirement to ask the user for a supported analysis window on write plans, and clarification that the limit does not apply to campaign scheduling dates. This is rich context an agent could not infer from annotations or schema.

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?

Purpose is front-loaded in the first sentence, and subsequent sentences follow a logical constraint-then-procedure order. The ratio-recomputation and keyword-trend caveats are dense but each carries distinct information; minor redundancy around repeated 95-day language prevents a 5.

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, return values need not be explained, and the description thoroughly covers the trickiest complexity (date-window handling and ratio aggregation). It is nearly complete, with the only gap being explicit tool-selection guidance against the many sibling advertising query tools.

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%, so the baseline is 3, but the description adds meaningful semantics for startDate/endDate beyond the schema: exact splitting rules, independence of comparison ranges, and the distinction between reporting vs scheduling date limits. It does not elaborate on limit/offset/sortBy beyond the schema, keeping it at a 4.

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?

The first sentence states a specific verb ('Returns') and resource ('store-level advertising performance or paginated advertising performance metrics grouped by SKU, ASIN, or parent ASIN') scoped to a single store and date range. It is clear what the tool produces, though it does not explicitly contrast itself with siblings like query_advertising_campaigns or diagnose_ad_efficiency.

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 provides extensive operational usage guidance for date ranges (95-day windows, non-overlapping splits, separate limits for keyword ranking trends, no auto-splitting of write plans). However, it never states when to choose this tool over sibling query/diagnose tools, so selection guidance is only implied by the resource name.

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