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

No annotations are provided, so the description carries the full burden. It discloses that the tool returns full product details and prices from multiple merchants, which is the primary behavioral output. It doesn't mention failure modes or network dependencies, but for a simple lookup tool this is adequate.

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 two concise sentences, front-loaded with the verb 'Look up' and the resource 'product'. Every word adds value, with no fluff or redundancy.

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 simple lookup tool with two optional-looking parameters and no output schema, the description is sufficient. It states the high-level return payload. The only minor gap is not clarifying which parameter to prefer, but the schema describes 'ean' as an alternative name, partially covering this.

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%, with both parameters (ean and barcode) documented. The tool description adds no extra parameter semantics beyond what the schema already provides, so a baseline score of 3 is appropriate.

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 tool does a product lookup by EAN/UPC barcode, a specific verb+resource combination. It distinguishes itself from sibling tools like product_search and price_comparison by focusing on barcode input, making the purpose unambiguous.

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 clear context: use this tool when you have an EAN/UPC barcode. It doesn't explicitly list alternatives or exclusion criteria, but the barcode-specific wording makes the intended use case obvious, qualifying as clear context without exclusions.

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