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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, so the safety profile is covered externally. The description adds genuinely useful behavioral context beyond that: each marketplace contributes roughly 8-13 top reviews and up to 5 marketplaces can be merged, which sets result-volume expectations.

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?

The purpose sentence is front-loaded and the parameter notes are terse and example-driven with no filler. Slightly fragmented formatting (trailing blank line, sentence fragment style) keeps it from a 5, but every sentence earns its place.

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 four parameters, no output schema and no enum guidance, the description leaves meaningful gaps: the `stars` filter format and `verified_only` behavior are unaddressed, and return-shape expectations (per-marketplace review lists plus topic sentiments) are only gestured at. What it covers it covers well, but it is not complete for this parameter set.

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 0%, so the description carries the full burden, and it only documents two of four parameters. It does add real value for those two (ASIN-or-URL format with an example for product; comma-list syntax and a per-marketplace review estimate for marketplaces), but `stars` and `verified_only` are left completely unexplained, including the ambiguous string format of `stars`.

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?

The description states a specific resource and behavior: Amazon top reviews merged across marketplaces, plus "Customers say" topics with sentiment. That is far more specific than the name alone. It differentiates itself from the walmart_* siblings implicitly through the Amazon scope, but never names them, 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?

Usage is implied by the platform scope (Amazon reviews vs walmart_reviews), but there is no explicit when-to-use or when-not-to-use guidance, and no stated prerequisites or alternative selection logic. An agent can infer the intent, but the description does not route it.

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