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: it discloses per-call credit cost, that repeated calls may charge again (consistent with idempotentHint=false), and that returned data should be treated as untrusted. These are non-obvious operational and safety facts an agent needs.

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 sentences, front-loaded with the core purpose, followed by cost and trust notes. Every sentence earns its place, though the cost wording is slightly repetitive ('Default cost' vs 'actual cost follows your plan').

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?

No output schema exists, but the description covers purpose, cost, idempotency implications, and data-trust posture, and returnFields is documented in the schema. Missing only return-shape or pagination hints, which is minor for this scope.

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 the schema already documents all six parameters, including the compatibility-only newProduct and the returnFields behavior. The description adds no parameter-level meaning, so the baseline 3 is appropriate.

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 clear verb ('Retrieve') and a specific resource ('listing growth and launch trends for a category'), which an agent can distinguish from adjacent siblings like amazon_market_shelf_time or amazon_market_statistics. It does not explicitly name or contrast those siblings, so it stops 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 never says when to use this tool versus the many sibling market/trend tools, nor does it state prerequisites or exclusions. It only gives cost mechanics, not selection guidance.

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