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

Beyond the readOnly and idempotent annotations, the description discloses deduplication, concurrent fetching, pricing per ASIN including not-found results, a 413 error for over 20 ASINs, the caveat about multi-variant listing data, and the meaning of null fields. This is substantial behavioral context that annotations alone would not provide.

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 compact yet information-dense: it states the tool's relationship to product_details, the core behavior, pricing, limits, and important data caveats in a few sentences. Every sentence adds useful information without padding.

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 does, when to use it, cost, limits, error behavior, data quality caveats, and response field meanings. Given that an output schema exists and annotations cover safety, nothing essential is missing for an agent to select and invoke this tool correctly.

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 input schema already fully documents all four parameters, so the baseline is 3. The description adds valuable semantics by explaining that ASINs are deduplicated, that billing applies even to not-found ASINs, and that bullet/spec fields may describe the product family rather than the exact variant.

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 verb ('fetches'), a resource (product details for ASINs), and a defining constraint (up to 20 ASINs per call). It explicitly identifies itself as a 'Batch variant of product_details', which immediately distinguishes it from the sibling 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?

The description clearly establishes when to use this tool: for multiple ASINs, because it is 'far cheaper and faster than N single calls', and the 20-ASIN limit sets a boundary. It does not explicitly name the alternative tool for single calls, but 'Batch variant of product_details' makes the alternative obvious.

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