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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds genuine output context — sales counts per country, median price in EUR for two countries, the price gap, and a link to the full comparison — which an agent cannot derive from annotations or schema.

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 sentences, each carrying distinct information: what is compared, what is returned, and who it is for. The output shape is front-loaded before the audience note, with 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, the description does the necessary work of summarizing return values (counts, medians, gap, link). The remaining gap is query semantics — it is unclear whether query is a keyword, phrase, or category — for a 2-parameter tool with one required free-text input.

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 50%: home_country is fully documented in-schema including the 'FR if unknown' fallback, but query has no description at all. The description only implies query is a search term ('The same search') and clarifies that median price is reported for the home country plus the next busiest, adding some meaning to home_country beyond the enum.

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 states a specific verb and resource — running one search across all 7 Vinted countries and comparing sales counts and median EUR prices — which is clearly distinct from a single-market price lookup. It never names the sibling vinted_sold_prices, so differentiation is inferable but not explicit.

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?

'Useful for cross-border reselling' gives a usage context, implying it fits market-selection decisions. However there is no explicit when-to-use vs. vinted_sold_prices, no prerequisites, and no statement of when a single-country lookup is preferable.

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