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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds behavioral context beyond that: the comparison dimensions returned, that shared materials are computed, and that scento.com links follow the user's language while answers stay English. Some of the return enumeration overlaps the existing output schema, which slightly dilutes the added value.

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?

Two sentences, front-loaded with the trigger condition and followed by exclusions. The long enumeration of returned fields ('house, Scento family, top, heart and base notes, shared materials, character, seasons, hours, year and concentration') is heavy and partially redundant given the output schema, but the rest is tight and earns its place.

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 two-parameter read-only comparison tool with full schema coverage and an output schema, the description supplies everything missing: trigger phrasing, cardinality limits, sibling disambiguation, language behavior and return breadth. An agent has enough to select and invoke 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 description coverage is 100%: both `perfumes` (2-4 items, name or slug, with examples) and `lang` (enum values, default, language semantics) are fully documented in the schema. The description corroborates the 2-4 constraint but adds no syntax or format detail beyond it, so the baseline of 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 verb and resource ('compare... two to four named perfumes, fragrances or colognes') and enumerates trigger synonyms (versus, vs, difference between, which one). It also names the sibling tools it is not (scent-neighbours, perfume-search, perfume-portrait), so an agent can distinguish it 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?

Explicit when-to-use ('user asks to compare, contrast or choose between two to four named perfumes') and explicit when-not-to-use with the correct alternatives named for each exclusion case. Nothing is left to inference.

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