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

Adds real context beyond annotations: cost per successful call, repeat-call billing, and the untrusted-data warning. The repeat-charge note is consistent with idempotentHint=false and is exactly the kind of caveat an agent needs. It stops short of describing pagination or result-set behavior, which matters for a list tool with a size parameter.

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 tight sentences, front-loaded with the action and followed by cost and trust caveats. No filler, though the space saved could have been spent differentiating it from its sibling.

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 should hint at the payload shape, but 'comparable product records' is undefined and there is no mention of pagination, default result count, or what fields returnFields can request. Adequate for billing and safety, thin on what an agent will actually get back.

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 coverage is 100%, so asin, size, marketplace, and returnFields are all documented in the schema already. The description adds no parameter meaning beyond a vague 'comparable' framing, so 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 and resource: 'Retrieve comparable product records for an ASIN.' That is clear enough to act on, but it does not distinguish this tool from the near-identical sibling amazon_product_competitor_lookup, leaving the agent to guess which competitor endpoint to use.

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?

No guidance on when to use this versus amazon_product_competitor_lookup, amazon_asin_detail, or the market_* siblings. The only conditional information given is billing-related, not selection-related.

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