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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the bar is lower. The description adds meaningful behavior beyond that: it states the validation logic (check-digit, GS1 prefix) and what the response surfaces (validated records, brand, claim status).

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 compact, front-loaded with the core question, and contains no filler. Every phrase contributes information about what the tool checks or returns.

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 present and annotations covering safety and idempotency, the description gives enough context for a single-parameter lookup: what to pass, what validation is performed, and what data comes back. No critical gaps remain.

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% and there is only one required parameter, so the description must carry the meaning. It does: the parameter is a GTIN, and the description explains that it will be validated by check digit and GS1 prefix. It stops short of specifying exact GTIN format or leading-zero handling, but for a single obvious identifier this is adequate.

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 opening question frames the tool's purpose clearly: verifying whether a GTIN is real and whom it belongs to. The description names the concrete checks (check-digit validation, GS1 prefix) and the returned context (records, brand, claim status), which distinguishes it from the lookup/get siblings.

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 the use case—when you need to validate a GTIN and find associated records—but it never explicitly says 'use this when...' or contrasts it with siblings like get_item, get_label_and_claims, or find_verified_supplier. There is no exclusion guidance, so it remains at the mid range.

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