nutriscore_nova

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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds genuinely useful behavior beyond that: missing scores return null rather than raising an error, each value comes with a one-line meaning, and an explicit 'not medical or dietary advice' disclaimer sets expectations for interpretation.

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?

Three short sentences, front-loaded with the return contract, then the null-on-missing rule, then the disclaimer. No filler and every sentence carries distinct information an agent would act on.

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?

There is no output schema, so the description carries the return contract itself and does so completely: field meanings, letter and group ranges, and null handling for missing data. Combined with annotations and a fully documented single parameter, nothing an agent needs to call this correctly is absent.

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 100% and the single barcode parameter is fully documented in the schema (EAN-8/UPC-A/EAN-13, digits only, separators ignored). The description only reinforces the cardinality constraint ('one barcode'), so the baseline 3 applies with no meaningful semantics added.

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 gives a specific verb+resource: returns the Nutri-Score letter and NOVA processing group for a single barcode, and even defines both scales inline (A best–E worst; 1 minimally processed–4 ultra-processed). An agent can tell this computes derived ratings rather than raw nutrient data, which separates it from nutrients_per_serving and barcode_lookup, though no sibling tool is named explicitly.

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 phrase 'for one barcode', which hints that multi-product comparison belongs to compare_products, but there is no explicit when-to-use or when-not-to-use guidance. The reader must infer that this is the scoring tool versus the raw lookup and search siblings.

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