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

Annotations cover the safety profile (readOnly, non-destructive), so the description correctly spends its words elsewhere: it discloses the credit cost, warns that repeat calls re-charge (consistent with idempotentHint=false), and flags returned data as untrusted. That is real value beyond the structured fields.

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?

Short and front-loaded: the operation comes first, then billing, then a safety note. Every sentence carries information; minor deduction only because the billing sentence is slightly verbose.

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 tool with full schema coverage and no output schema, the description covers cost and trust well but says nothing about the shape or granularity of the historical trend data returned, which is the main thing an agent might need to reason about.

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 each parameter is documented in the schema itself, so the description is not required to carry this load. It adds nothing about the ASIN format, marketplace enum, or returnFields syntax. Baseline 3.

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 historical coupon activity for an ASIN.' An agent immediately knows the operation. It does not, however, distinguish itself from the close sibling amazon_asin_with_coupon_trend, which appears to cover similar territory.

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_asin_with_coupon_trend, amazon_asin_history, or amazon_asin_sales_trend. The only 'usage' content is billing mechanics, not tool selection context.

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