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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds the inventory of returned fields and the equivalence to get_health.marketplaces, which is useful behavioral context beyond the annotations. It says nothing about caching, ordering, or whether the list is static, but for a small read-only lookup that is minor.

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 purpose and return fields, then the cross-tool usage hint. No filler or redundant restatement of the title.

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?

There is no output schema, but the description compensates by naming the returned fields, and with zero parameters and covered annotations nothing else is needed to call it correctly. The equivalence note to get_health closes the main remaining question about redundant sources.

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?

The tool takes no parameters, so there is nothing to disambiguate and the baseline is 4. The description correctly omits parameter discussion rather than inventing any.

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 (domain, label, currencyHint, tagConfigured), so the agent knows exactly what comes back. It also explicitly notes the data is identical to get_health.marketplaces, which cleanly separates it from that sibling.

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?

Gives concrete downstream guidance: pass the user's marketplace (amazon.com for US, amazon.se for Sweden) on search/catalog/resolve/create, which tells the agent both when to call this and what to do with the result. It does not explicitly say when to skip this tool, though the get_health equivalence implies a fallback.

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