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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and determinism are covered. The description adds genuinely new behavioral context: the lookup is a fallback chain across two external databases before the ingredient check, which annotations cannot express. It does not cover failure behavior for an unknown barcode.

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 short sentences, front-loaded with the action before the implementation detail. Efficient, though 'checks its ingredients' is slightly vague about what the check yields.

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 simple single-parameter read tool the description is serviceable, but with no output schema it gives no hint of the return shape (ingredient verdicts, unknown-product handling, which source answered). Something an agent needs to interpret results is missing.

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?

There is a single required parameter with 100% schema description coverage ('EAN-13, EAN-8 or UPC barcode digits'). The description adds nothing about the barcode format beyond the schema, so the baseline of 3 is appropriate.

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 and resource ('Check a product by barcode') and names the exact data sources it queries (Open Food Facts, then Open Beauty Facts) plus the ingredient check. It is clear what the tool does, though it does not distinguish itself from the sibling check_ingredients, which sounds like an overlapping capability.

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?

Usage is only implied by the name and the word 'barcode'. There is no statement of when to prefer this over check_ingredients, search_products, or check_medicine, nor any prerequisite or exclusion. An agent must guess at the routing.

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