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

Annotations already cover readOnly/idempotent/non-destructive, and the description adds genuinely new behavioral facts: alias matching (arachis oil, casein, Latin names) and that 'free from' marketing claims are not trusted. It does not describe the shape of the result, which matters since there is no output schema.

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 action and the alias-catching behavior before the usage directive. Slightly padded by the closing sentence, which re-lists 'food, cosmetic or household product' already implied by 'Covers food and cosmetics'.

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?

Given three parameters at full schema coverage and rich annotations, the only real omission is what the response contains (per-person verdicts? matched ingredients?), which is not covered by any output schema. Otherwise an agent has everything needed to call 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?

Schema description coverage is 100%, so the schema already explains ingredients, household entries, per-person allergens and severity. The description adds conceptual color (household = multiple people, hidden ingredient names) but no parameter-specific guidance beyond that, so the 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?

Specific verb (check) plus a precisely scoped resource (a product's ingredient list against the allergens of one or more household members). The mention of alias detection and coverage of both food and cosmetics clearly separates it from lookup_ingredient and list_supported_allergens.

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?

Explicit triggering condition: 'whenever the user asks if a product or ingredient list is safe' plus a proactive directive ('even if the answer seems obvious', 'before recommending or buying'). It does not name when NOT to use it or point to lookup_ingredient / list_supported_allergens as alternatives, which keeps it short of a 5.

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