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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false, openWorldHint=true), so the description correctly focuses on other behavior: a concrete credit cost per successful call, plan-dependent actual cost, repeat-charge behavior consistent with idempotentHint=false, and an explicit 'treat returned data as untrusted' warning. These add real context beyond the structured fields; only the response/pagination shape is left unaddressed.

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 sentences, front-loaded with purpose, followed by cost and a trust note — no filler and each sentence carries distinct information. Slightly terse for a 45-parameter tool, but nothing 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?

For a highly complex 45-parameter tool with no output schema, the description covers purpose, cost, and data-trust but never sketches the return shape or pagination, which the metric enumeration only implies. It is adequate minimum-viable coverage given full schema descriptions, but not rich.

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 45 parameters are documented in the schema itself (including pagination, bid ranges, and filter bounds). The description adds no parameter-level meaning beyond repeating the metric categories, so the 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 ('Research') and resource ('keyword') and enumerates the metric domains it returns: demand, growth, competition, conversion, and PPC. This is clear on its own, but it does not distinguish itself from close siblings like amazon_keyword_research_trends or amazon_keyword_conversion, so an agent cannot tell the overlapping keyword tools apart from this text alone.

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?

There is no when-to-use, when-not-to-use, or alternative-routing guidance despite a large family of keyword siblings. The only usage-adjacent content is billing ('Repeated calls may charge again'), which informs cost behavior rather than tool selection.

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