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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=false), and the description adds genuinely new operational context: pagination is 25 rows per page, the data source is observed buy-box data, and the tool is restricted to Amazon marketplaces. It does not detail sorting defaults or empty-result behavior, so not a full 5.

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?

Dense but front-loaded: the resource and pagination lead, then per-kind definitions, then usage guidance. Every clause carries information, though the per-kind enumeration makes individual sentences long and slightly harder to scan.

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 an 8-parameter, five-mode tool with no output schema, the description supplies the mode semantics, ranking fields, marketplace scope, pagination and routing to follow-up tools, which is sufficient for an agent to select and invoke it correctly.

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 75%, and the description meaningfully augments it by mapping the valid sort values to each kind (e.g. top_brands by buybox_days/sellers/control_score/asins/revenue/amazon_share) and clarifying window and direction semantics for the movers kinds. It adds real value beyond the schema's terse field descriptions rather than restating them.

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 resource (ranked discovery lists from buy-box data) and then enumerates all five modes with the exact metric each ranks by, so an agent can distinguish brand_movers, seller_movers, top_brands, top_sellers and top_categories without opening the schema. It also differentiates from siblings by declaring itself the discovery entry point versus drill-down tools.

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?

Explicitly frames the use case ('Use to DISCOVER brands, sellers or categories - sourcing leads, brands under seller pressure, the biggest resellers') and names the natural follow-ups (evaluate_brand, seller_profile, category_metrics), plus scoping to 'Amazon marketplaces only'. It stops short of an explicit when-not/exclusion statement, which keeps it below a 5.

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