get_package_dimensions

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

Annotations already establish readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context beyond annotations: it costs 1 credit, returns structured fee-category data rather than a human-readable string, and is designed for fee calculation. The only omission is a more detailed return format description, but that burden is reduced by the present annotations.

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 three sentences with no wasted words. It front-loads the tool's output, then covers usage guidance, the alternative tool, and credit cost. Every sentence contributes a distinct piece of decision-relevant information.

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?

For a low-complexity tool with two parameters, full schema coverage, and clear annotations, the description is sufficient. It explains what the tool returns, when to use it, when not to use it, how it differs from the nearest sibling, and that it costs one credit. No critical selection or invocation context is missing.

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 the baseline of 3 applies: the schema fully documents asin and domain, including format, examples, defaults, and marketplace meaning. The description does not add parameter-specific semantics beyond what the schema already provides, which is acceptable given the complete schema coverage.

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 begins with a specific verb and resource: 'Get a product's precise physical and logistical attributes' and explicitly names the package dimensions and fee category. It also positions the tool as 'the FBA fee-estimation and shipping-cost tool,' which clearly distinguishes it from siblings like get_product_detail.

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: shipping, storage, FBA fees, or warehouse planning. It also provides a clear when-not-to-use and names the alternative: 'Do NOT use it for general product info — get_product_detail includes a human-readable dimensions string, but only THIS tool returns the structured fee category and exact measurements.' This is model guidance.

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