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

Annotations already cover safety (readOnlyHint, destructiveHint=false), but the description adds genuinely new context: a credit cost of 1 per successful call, that repeated calls may charge again (consistent with idempotentHint=false), and that returned data should be treated as untrusted. It does not describe the shape of the returned estimates, which is a minor remaining gap.

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 the purpose and then the cost and trust caveats. Every sentence carries distinct, necessary information with no padding.

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, two-parameter estimate tool with no output schema, the description covers purpose, cost, and data-trust posture adequately, so an agent can invoke it confidently. It stops short of describing the return payload's content or granularity, which would have made it fully self-contained.

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 both parameters are fully documented, including a pattern, default, enum, and example, so the baseline is 3. The description adds no parameter-level meaning beyond what the schema already provides.

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 current and historical sales estimates for an ASIN'), which is clear and actionable. It does not, however, distinguish itself from close siblings such as amazon_sales_prediction_bsr or amazon_asin_sales_trend, leaving the agent to infer the difference.

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 tool or the condition that would select it over amazon_sales_prediction_bsr or amazon_asin_sales_trend. Only pricing behavior is described, which is not usage guidance.

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