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

Annotations already cover the safety profile (readOnlyHint, openWorldHint), so the bar is lower, and the description adds meaningful context: the newest matching DSLD label is returned normalized alongside older versions. It does not state what happens when no label matches or how multiple products are disambiguated, leaving a small gap.

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?

Two tight sentences, zero filler, with the identifying action and identifier front-loaded ahead of the return-value note.

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 no output schema, the description usefully discloses the return shape (newest normalized DSLD label plus older versions), which is exactly the missing structured information. Only the no-match/empty-result case is left unexplained for an otherwise simple single-parameter lookup.

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% and there is only one parameter, so the schema already documents the UPC-A/EAN format, length, and space/dash handling. The description only reinforces that the code is printed on the bottle, adding marginal value beyond the schema; baseline 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?

States a specific verb ('Look up') and resource ('supplement by UPC/EAN barcode'), and implicitly distinguishes itself from products_search and products_get by naming the exact identifier used. An agent can tell this is the barcode-keyed retrieval tool without opening any schema.

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 'barcode printed on the bottle' implies the trigger condition for using this over products_search, but no alternative is named and there is no explicit when-not guidance. Usage is inferable, not stated.

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