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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description still adds real behavioral context beyond them: prices are 'vigente' (current), comparisons never cross currencies, and results are expressed as distance from the cheapest store plus per-currency dispersion. It does not say what happens when the product is published in zero or one store.

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 short sentences: what is compared and what is reported first, then the currency constraint as its own line, then where the IDs come from. Nothing is redundant and the most decision-relevant constraint is front-loaded.

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 only two parameters, rich annotations and no output schema, the description carries the burden of conveying the return shape, which it does at a high level (deviation from cheapest, dispersion per currency). It is nearly complete; missing only edge-case behavior (no stores, single store, mixed-currency output grouping).

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 both parameters are already documented, which sets a baseline of 3. The description goes beyond it by stating provenance (the IDs come from radar_search_listings) and by clarifying that variantId is optional and narrows the comparison to a single variant.

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?

Names a specific verb and resource (compare the current price of a canonical product across all stores where it is published) and adds what the result expresses: deviation from the cheapest store and dispersion per currency. It does not name a sibling explicitly, so an agent must infer the boundary with radar_get_product_prices or radar_compare_substitutes from the scope wording alone.

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 clear usage context (a canonical product of your organization, across every store where it is published) and an explicit prerequisite: the productId/variantId come from radar_search_listings. It also carries a hard constraint — never compares different currencies — without naming an alternative tool for cases that fall outside this scope.

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