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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the 'Read-only' sentence is largely redundant. The description does add real value by naming the payload fields, which is the only source of return-shape information since no output schema exists. It stops short of saying what happens for an untracked ASIN (error vs empty), which would be the remaining behavioral detail.

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 short sentences, front-loaded with what is returned, then the safety hint, then the sibling routing. No filler or repetition of the schema.

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 field enumeration is essential and present, and sibling routing is covered. A minor gap remains around not-found behavior and whether the snapshot is timestamped, but the agent has enough to call it 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?

Schema description coverage is 100% and the single asin parameter is documented as a 10-character Amazon ASIN, so the schema carries the load. The description only restates 'by ASIN' and adds no format, casing, or multi-ASIN guidance beyond it. Baseline 3 for a fully described single parameter.

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?

Specific verb+resource ('Returns one tracked product by ASIN') with the key lookup key stated up front, then an enumeration of the returned fields (category, image, stock, seller count, latest listing snapshot). This is clearly distinguishable from get_product_metrics (series data) and list_products (scan).

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?

Explicitly routes to alternatives with their conditions: get_product_metrics for the price and BSR series, list_products to scan the account. An agent can pick the right tool without opening any schema.

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