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

Annotations already establish this as a safe, idempotent, closed-world read, so the bar is lower; the description goes well beyond them by disclosing the divergent return shape (rda/upper_limit for nutrients vs supplement/what_studies_looked_at/studied_amounts/ceiling/cautions/source for supplements) and the country=GB NHS-amount and uk-field behavior. It does not cover failure handling for unrecognised names, but the substantive behavior is disclosed.

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 purpose is front-loaded and every sentence carries information, though the opening "Supplement Check." merely echoes the name and the long nutrient enumeration makes the middle sentence dense. It is appropriately sized for the breadth of inputs it must define.

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 carries the return-value burden and does so: it lists the response fields, explains the supplement-vs-nutrient branching, and describes country-specific output and the NIH fact sheet link. 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 coverage is 100%, so the baseline is 3. The description adds value by effectively enumerating accepted `name` values (vitamins A–K, minerals, and named supplements) and forms, compensating for the absence of any enum in the schema, and by clarifying the GB/NHS effect of `country`.

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 names a concrete resource (vitamin/mineral/supplement facts: what it does, adult amounts, limits, cautions, food sources) and gives example phrasings, so the tool's function is unmistakable. However, it never differentiates itself from the similarly named siblings supplementcheck_get_supplement and supplementcheck_check_dose, so an agent must guess which of the three to call.

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?

Example queries ("what does magnesium glycinate do?", "is ashwagandha safe?", "how much vitamin D do I need?") give clear positive usage context. There are no explicit exclusions or pointers to the alternatives, which is a real gap given the overlapping sibling names.

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