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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description usefully discloses the return shape (one winner per size), which matters since there is no output schema, but says nothing about missing sizes, partial data, or how the optional size parameter alters behavior.

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?

Two tight sentences with the core behavior front-loaded and the caveat second. No filler, though it could more directly anchor the optional size parameter.

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 per-size-winner statement carries important return-value context, and annotations cover safety. Still missing is how the optional size argument interacts with the 'EACH size' behavior—an agent cannot tell whether it returns all sizes or just the filtered one.

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 coverage is 100%, so both parameters are already documented, and the description adds only the concept that results are per-size. It does not clarify what happens when the optional 'size' filter is supplied versus omitted, which is the one ambiguity the schema cannot resolve.

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 resource and operation: the cheapest retailer per size for one product. The second sentence sharpens the distinction from a product-level lowest-price query, though no sibling tool (e.g. where_to_buy) is named for contrast.

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?

Gives a usage condition by warning that a product-level 'lowest price' is usually wrong for a specific buyer, which implies when to prefer this tool. However, it never names an alternative among the siblings (where_to_buy, search_sneakers) or states explicit exclusions, leaving routing to inference.

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