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

Annotations already declare readOnly and non-destructive, so safety is covered. The description adds genuinely non-obvious behavior: the found:false / exhaustive:false combination does not mean the product is absent, and SKU lookups may resolve to a variant rather than a product — semantics an agent could easily misread from the output schema 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?

Three sentences, each doing work: the operation, the parameter hierarchy, and the failure-mode caveat. Front-loaded and free of filler, with only minor overlap between the SKU/handle sentence and the schema descriptions.

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 an output schema and read-only annotations already present, the description supplies what structured fields cannot: the exclusivity rule and the interpretation of the ambiguous found/exhaustive result pair. The one gap is that the 'source' parameter is delegated entirely to search_products rather than described here.

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 all five parameters are already documented, including the source enum and includeVariants default. The description's one real addition is the implicit 'exactly one of' exclusivity constraint, which the schema does not encode (no oneOf), but the rest restates schema content.

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?

Opens with a specific verb and resource ('Look up a single product in full') and immediately constrains the scope to exactly one of three lookup keys. It is clearly distinct from search_products, which it references as the underlying mechanism for SKU/handle resolution.

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 actionable selection guidance among the three lookup parameters, explicitly recommending productId as the reliable path and flagging SKU/handle as slower, possibly many-to-one lookups. It stops short of stating when to prefer search_products first or when this tool should not be used.

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