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

Beyond the readOnlyHint annotation, the description discloses key behaviors: it fetches nothing without a marketplace parameter, returns money in the marketplace's local currency, and has a strict mandatory output contract for Account notice paragraphs. These are material behavioral details that an agent could not infer from the annotations alone.

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 description is front-loaded with the core purpose, then organized into clear labeled sections: usage, marketplace handling, and output contract. The longer output-contract section is justified because it imposes a critical, mandatory response behavior that cannot be paraphrased or omitted.

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?

The description covers what the tool returns, how to invoke it correctly, the critical marketplace prerequisite and failure mode, currency semantics, and a mandatory output contract. Since there is no output schema, the description also names the main data fields, making it complete enough for an agent to call the tool correctly and process its response.

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% and the schema already explains ASIN requirements, marketplace codes, the 'MARKETPLACE NEEDED' failure, and currency context. The description reinforces these points and adds the 'ask once, reuse' instruction, but most parameter meaning is already carried by the input schema, so the description does not add substantial new parameter-level semantics.

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 names the exact operation — side-by-side raw data for 2–5 Amazon products by ASIN — and lists concrete metrics (price, sales/revenue estimates, reviews, listing quality, history). It also explicitly contrasts with analyzeProduct for single ASINs, which distinguishes it from a 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?

The description gives explicit when-to-use guidance: 2–5 ASINs for this tool, a single ASIN should use analyzeProduct, and this tool is a pure data fetch where the agent must perform the comparison itself. It also provides a clear conditional workflow for determining the marketplace, including 'ask once and reuse' and the 'MARKETPLACE NEEDED' failure mode.

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