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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds valuable context about the data returned (specific fields) and dataset scale ('6K+ products'). It does not contradict annotations and provides meaningful behavioral detail beyond the structured metadata.

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 a single, efficient sentence that front-loads the core purpose and lists the return fields without waste. The '6K+ products' note adds useful scale context without bloat.

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?

Given the presence of an output schema and comprehensive annotations, the description covers everything needed for correct invocation: purpose, parameter usage, and return scope. No critical information 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?

The schema description for the barcode parameter is comprehensive (format, example, range). The tool description adds no additional parameter semantics beyond what the schema already provides. Since schema coverage is 100%, the baseline of 3 applies.

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 clearly states the action (Lookup), the resource (cosmetics/personal-care product by barcode), and enumerates the returned fields (name, brand, categories, quantity, full ingredients list, image). It distinguishes from the sibling search tool by specifying 'by barcode' and from food.product.barcode by specifying 'cosmetics/personal-care'.

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 implies usage when a barcode is available, which is clear from the tool name and phrase 'by barcode'. However, it does not explicitly mention when to use the alternative search tool (openbeautyfacts.product.search), leaving the routing to inference. Still, the condition is straightforward.

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