lookup_product

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

Annotations already declare the operation read-only and non-destructive; the description adds non-obvious behavioral facts: wrong identifier_type matches return nothing, and each call costs 1 credit. It doesn't describe response details beyond 'essential product snapshot', but the annotations lower the burden.

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 purpose, followed by when-to-use, parameter rules, and the sibling alternative. Every sentence adds actionable information without padding.

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 conversion tool with no output schema, it explains the output (ASIN plus product snapshot), the key failure mode, cost, marketplace domain handling via schema, and the correct alternative for keywords. This is enough for an agent to select and invoke it correctly.

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 covers all 3 parameters, and the description adds valuable semantic detail beyond it: UPC is 12 digits, EAN/GTIN 13, ISBN 10/13, and matching identifier_type is mandatory. This extra guidance helps the agent construct correct calls.

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 states a specific conversion task — external product identifiers (UPC, EAN, GTIN, ISBN, JAN, MINSAN) to Amazon ASIN — and clearly distinguishes itself from sibling search_products by saying keywords should go there. It also notes ASIN validation as a secondary use, which further clarifies scope.

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?

It gives explicit when-to-use guidance ('Use this tool when the user has a barcode or standard product code'), describes typical workflows, and names the alternative for non-code inputs ('use search_products instead'). This is unambiguous routing.

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