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

With no annotations, the description carries the full burden and does so: it discloses the returned fields (status, maximum, conditions, required label warning, source URL, date checked), the data provenance (official MFDS/CosIng/FDA records), a citation obligation, and an explicit interpretation caveat that this is not a safety rating or medical advice. That is substantially more than the structured fields supply.

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 is front-loaded and every later sentence carries operational weight (routing, attribution, disclaimer). The first sentence is a dense run-on list that packs four region/return items into one clause, which slightly taxes readability, but there is no filler.

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 and no annotations, the description must explain both what comes back and how to interpret it, and it does: per-region status/maximum/conditions/warning/URL plus functional-cosmetic amounts, along with the citation requirement and scope limits. Nothing an agent needs in order to call or report this tool 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 coverage is 100% for the single 'name' parameter, so the baseline would be 3. The description earns above baseline by expanding accepted identifier types to INCI, common, trade, Korean name, or slug, which is a meaningful widening of the schema's terse 'ingredient name or slug'.

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 opens with a specific verb+resource ('One cosmetic ingredient') and enumerates exactly what is returned: per-region rules (Korea MFDS, EU CosIng, U.S. FDA) plus Korea's functional-cosmetic listing. It explicitly distinguishes itself from the sibling search_ingredients, so an agent can route correctly without opening any schema.

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?

It names a concrete alternative and the condition that selects it: 'Use search_ingredients first if the name is ambiguous.' That is a real routing rule, not an implication. It stops short of stating exclusions (e.g. when to prefer check_ingredient_list or get_product instead), so it is strong but not exhaustive.

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