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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds real value beyond them: a concrete credit cost per successful call, the warning that repeated calls may charge again (consistent with idempotentHint=false), and a trust warning about returned data. It stops short of describing pagination or return shape, so not a 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?

Three tight sentences: purpose first, then billing semantics, then the trust warning. Nothing is repeated from the schema and every sentence carries information the agent needs.

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 lookup with full schema coverage and no output schema, the description covers what is returned, the cost model, and the trust caveat. It does not mention pagination limits or month defaulting, which is a minor gap but not a blocking one.

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 every parameter (asin, page, size, month, marketplace) is already documented in the schema with patterns, defaults and enums. The description adds no additional parameter meaning such as default month behavior or marketplace implications, 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 ('Retrieve') plus the resource ('traffic keywords, demand, and rank positions') and the input key ('for an ASIN'), so the agent knows exactly what it gets back. It does not differentiate itself from near-name siblings like amazon_traffic_keyword_stat or amazon_traffic_source, so it falls short of a 5.

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?

The description gives no when-to-use guidance and never names an alternative among the many traffic/keyword siblings, so an agent cannot tell why it would pick this over amazon_traffic_keyword_stat or amazon_keyword_research. Cost information is present but that is not usage routing.

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