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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds real behavioral context beyond that: keyword fallback to a US catalog /dp product when one exists, Accept-Language-driven marketplace selection, and that unknown marketplace values fall back to amazon.se rather than erroring — valuable for invocation confidence.

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-loaded with the core action and output, and the storefront guidance is placed where it matters. It loses a point for repeating the marketplace fallback text that already exists verbatim-ish in the schema, which is redundant filler in the description.

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 9-parameter, no-required-params tool with no output schema, the description gives the return shape (product /dp vs packing search) and the resolution precedence, which is the essential missing piece. It stops short of explaining how climate/tripType/durationBand shape the packing-search branch, but the enums are largely self-describing.

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 67%, so the baseline is 3. The description elaborates the marketplace/country/Accept-Language precedence, but that chain is already spelled out in the marketplace schema description, and the remaining params (locale, climate, tripType, durationBand) are never mentioned, leaving their role in 'packing search' resolution undocumented.

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 (resolve) plus the accepted input forms (ASIN, /dp URL, keywords) and the concrete output (a buyUrl on a chosen storefront). This is distinguishable from siblings like get_catalog or search_packing_items, which do not produce a resolved buy link.

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 spends its guidance on which marketplace/storefront to choose (US users → amazon.com, default amazon.se), which is useful, but never says when to call this instead of siblings such as get_catalog, search_packing_items, or add_packing_item. Usage is implied by the input forms rather than explicitly routed.

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