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

Annotations already cover the safety profile (readOnlyHint, destructiveHint=false, openWorldHint=false), so 'Read-only' is a restatement. It does add real behavioral context: result composition (best 5 offers, EUR, French market), the historical minimum and price-history summary, and the cross-tool EAN dependency. Missing details like pagination or freshness/latency are minor.

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 dense sentences with the output contents front-loaded, then the EAN sourcing prerequisite, then usage triggers. Zero filler and no repetition.

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?

There is no output schema, yet the description enumerates what comes back (offers, historical low, price-history summary) plus market/currency scope and the upstream data source, so an agent has everything needed to call and interpret it.

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% for the single param, so the baseline is 3. The description reiterates that the product is identified by EAN and points at pryx_advice products[].ean, which is essentially what the schema field description already says — little added semantics beyond the structured data.

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 (returns) plus concrete resources (merchant offers, lowest price ever, price-history summary) for exactly ONE product, and pins scope with 'best 5, in EUR, French market'. This clearly separates it from pryx_advice (recommendations) and pryx_categories.

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 a clear when-to-use trigger ('answer "where is it cheapest?" or "is it a good time to buy?" after a recommendation') and a prerequisite chain ('Get the EAN from the `ean` field of pryx_advice results'). No explicit exclusions or named alternative tools are given, so it stops just short of a 5.

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