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

There are no safety annotations, so the description carries the burden. 'Look up' clearly indicates a read-only operation, and the list of returned fields (nutrition, Nutri-Score, processing) provides useful behavioral context beyond the tool name.

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 a single, well-structured sentence that front-loads the purpose and then enumerates the useful data fields. Every word earns its place with no waste.

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 one-parameter lookup without an output schema, the description adequately covers what the tool returns. It could mention error handling for invalid barcodes, but that is not essential for basic use.

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?

The schema already documents the barcode parameter with format and example, so description adds little beyond restating 'by its barcode'. With 100% schema coverage, 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?

The description uses a specific verb 'Look up' and clearly identifies the resource: a packaged food by barcode. It also lists the specific data returned, which distinguishes it from food_search and food_hygiene.

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 primary use case: when you have a barcode for a packaged food product. It does not explicitly mention alternatives or exclusions, but the context is clear given the sibling tools like food_search.

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