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

Annotations only cover readOnlyHint and openWorldHint, yet the description discloses the exact result shape (ASIN, title, price, rating, review count), separates organic from sponsored/brand/video ads, and warns that the ad list is inherently incomplete due to Amazon's bot filtering, advising 'seen advertising' framing. That is real operational context an agent could not derive from the annotations.

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?

Two sentences, front-loaded with purpose then output/limitation, with no filler. The second sentence is dense with three clauses, which slightly reduces scannability but every clause carries information.

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 fully carries the burden of describing return values and explicitly flags the reliability limitation of the ad portion. For a two-parameter read tool with only one documented parameter, nothing an agent needs 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 50% — marketplace is documented inline while keyword is not — and the description adds no format, length, or marketplace-behavior detail beyond the schema. It does not compensate for the undocumented keyword parameter, 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?

The description names a specific verb and resource ('See who ranks for a keyword on Amazon') and enumerates exactly what is returned: organic results in rank order plus ad placements. An agent can distinguish this from amazon_product (single product lookup) or amazon_keyword_gap (gap analysis) 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?

Usage is implied by 'See who ranks for a keyword', which signals a rank-tracking scenario, but there is no explicit when-to-use/when-not-to-use guidance and no sibling tool is named as an alternative. The ad-caveat is a presentation instruction rather than selection guidance, leaving the agent to infer when this beats amazon_keyword_gap.

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