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

Annotations already mark the tool readOnly and non-destructive; the description adds substantive behavior beyond that by stating 'Pure data fetch (no AI analysis)' and explaining the interpretation semantics of aggregates like revenueTop5SharePercent. This meaningfully shapes agent expectations about what the tool will and won't do.

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?

The description is longer than a minimal two-liner, but each clause earns its place: deliverable, no-AI caveat, and a decision framework. The most important information is front-loaded, though the 'How to use' section is dense enough to slightly reduce skimmability.

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 no output schema, the description compensates by listing the aggregate categories the agent will consume and explaining how to reason over them. It could be more explicit about the exact response shape or product fields, but it provides enough for an agent to select and invoke the tool 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?

The input schema already describes all 4 parameters with 100% coverage and details like marketplace enums, currency, ranges, and filter semantics. The description adds no parameter-level meaning beyond framing keyword as a niche, which is only lightly useful given the schema's completeness.

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 description names a specific resource ('Amazon niche/keyword') and a concrete deliverable: a market snapshot with top products by revenue and computed aggregates. It also separates itself from analytic siblings by calling itself 'pure data fetch,' which clarifies its role versus compare/analyze 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?

It gives a clear invocation context—when you want a market snapshot for a niche/keyword—and a rich 'How to use' section for judging niche attractiveness. It does not explicitly name alternative tools or state when not to use it, so it stops short of full routing guidance.

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