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

readOnlyHint and openWorldHint already declare the safety profile, so the description only needs to add context. It contributes the shape of the returned records and the cross-tool dependency, but says nothing about how many marketplaces exist, ordering, or stability of the list. Useful additive context, but not rich 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?

Two sentences, no filler, with the resource and returned fields front-loaded before the actionable instruction. Every clause 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 no parameters and no output schema, the description covers the essentials: what comes back and how it must be used downstream. Minor gaps remain around the meaning of individual fields and whether the list is static, but an agent can call this correctly as written.

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?

There are zero parameters, so there is nothing to disambiguate and the baseline is 4. The description's field enumeration describes return values rather than inputs, which is a bonus given no output schema exists, but it does not explain what fields like tagConfigured or currencyHint mean.

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 (list) and resource (supported Amazon storefronts) and enumerates the returned fields, so the agent knows exactly what this call yields. It also frames the tool's role relative to the siblings that consume its output (search/catalog/resolve), which differentiates it from every other tool in the group.

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?

"Agents MUST pick the user's marketplace and pass it on search/catalog/resolve" gives an explicit prerequisite workflow and names the downstream tools that need it. It stops short of stating exclusions (e.g., skip this call when the marketplace is already known or cached), so it is not a full when/when-not guide.

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