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

Beyond the readOnly/openWorld annotations it discloses non-obvious behavior: price-less cards return `price: null` and are retained rather than dropped, `proxy_country` defaults to the marketplace home country to keep currency consistent, and notably the billing model (one unit per result page, keep max_results modest). That cost/rate context is exactly what annotations cannot convey.

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?

Front-loads the return shape in the first sentence, then layers filtering, pagination, edge-case price behavior and billing, with no filler sentences. It is a dense single paragraph, but each clause adds information an agent can act on.

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 output schema, the description carries the full burden of describing returns and does so field-by-field, plus it covers the null-price edge case, default currency behavior and cost. Nothing material is missing for a 7-parameter search tool.

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 every parameter is already documented, and the description largely restates the sort enum and the proxy/marketplace currency defaults rather than adding new syntax or constraints. 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 specific verb (Searches) plus resource (any regional Amazon marketplace listings), and enumerates the returned card fields, so an agent knows exactly what it gets. It also distinguishes itself from the sibling amazon_product by handing off full-detail fetches to that tool.

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?

Explicitly routes detail lookups to `POST /marketplace/amazon-product`, which is genuine sibling differentiation against amazon_product. It also spells out how to filter, order and page, though it never says when to prefer this over ebay_search, walmart_search or google_shopping for product queries.

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