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

Annotations already declare this a safe, idempotent, non-open-world read. The description adds the return payload that annotations cannot convey: per-100g/100ml and per-serving values, four traffic lights, Nutri-Score, allergens and a Halal link. That is meaningful beyond the structured safety hints.

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?

Purpose first, then usage triggers, then return contents - a sensible front-loaded order. The redundant 'Plate Pal.' prefix duplicates the title and the return list is dense, but every clause carries information for an agent.

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 is the only source of return-value information, and it delivers a thorough enumeration of what comes back. Parameters are covered by the schema, and the safety profile by annotations, leaving little an agent needs that 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?

Schema description coverage is 100%, so both 'code' (8-14 digits) and 'servings' (0.25-20) are already fully documented. The description's embedded example barcode adds format intuition but no semantics beyond the schema, 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?

States a specific resource (nutrition for a packaged product) and a specific selector (by barcode), with UK traffic lights as a differentiator. This distinguishes it from platepal_get_food_nutrition (general food nutrition) and halalornot_check_product_by_barcode (halal screening of the same barcode), though it does not name those siblings 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?

Gives three concrete triggering queries ('is this barcode high in sugar?', 'how many calories in this?' after a scan, 'what's the salt in 5000157024886?') that make the use context unmistakable. It stops short of explicitly excluding the sibling tools, so it lands at clear-context rather than explicit-alternatives.

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