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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and non-destructive behavior, so the safety profile is covered. The description adds a useful cost signal ('FREE') beyond annotations but otherwise mostly restates the output that the existing output schema governs.

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?

It is a single, front-loaded sentence that leads with the 'FREE' signal and then the core action. It is appropriately sized, with only minor room to add essential parameter-precedence guidance 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?

An output schema exists, so the description need not explain return values. But for an 8-parameter tool with 0% schema coverage and no required parameters, the description leaves key gaps: what minimum input is needed and whether identifiers can be mixed.

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 0% across 8 parameters, so the description carries the burden. It helpfully enumerates identifier types (GTIN, EAN, UPC, JAN, ISBN, MPN, OE, SKU, ASIN) and 'natural-language product signals', mapping to several schema fields, but it does not explain that zero parameters are required, whether at least one identifier is needed, how multiple identifiers are prioritized, or what 'manufacturer' does.

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 uses a specific verb ('Normalize') and a concrete resource (identifiers like GTIN/EAN/UPC and natural-language signals) and states the output (a stable product identity key and domain). It is clearly distinct from sibling search/buy tools, though it does not explicitly name a sibling to differentiate itself from.

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 phrase 'before shopping or purchase decisions' implies when to use it, positioning it as a pre-purchase normalization step. However, it gives no explicit when-not guidance and does not name alternatives such as commerce_search or parts_search to route between.

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