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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds real context beyond that: the row grain ('one SB campaign row') and a freshness caveat ('recent ~3 days may be incomplete'). It does not discuss pagination behavior, but the schema covers next_offset and an output schema exists.

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 tight sentences: scope and metrics first, grain and freshness caveat second, routing/exclusions third. Every sentence earns its place with no filler or repetition of the title.

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 read-only, filtered list tool with full schema coverage, an output schema, and clear annotations, the description supplies the remaining pieces an agent needs: the metric scope, the row grain, the freshness limitation, and the sibling routing. Nothing required to invoke 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 100%, so all ten parameters including date defaults, sort enums, and pagination are already documented in the schema. The description adds no parameter-level detail beyond what is structured, which is the expected baseline when the schema does the heavy lifting.

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?

Names a specific verb+resource ('Sponsored Brands campaign performance') and enumerates the distinguishing metrics it returns (new-to-brand, branded searches, video views, detail page views). It explicitly contrasts itself with Sponsored Products metrics, ASIN-level TACOS, and product sales, so an agent can separate it from siblings without opening any schema.

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?

Provides an explicit positive trigger and an explicit negative trigger, and names the exact alternatives to use instead (get_campaign_performance/get_tacos/get_sales_and_traffic). This is a textbook routing instruction with no inference required.

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