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

With readOnlyHint=true already covering safety, the description still adds substantial non-obvious behavior: anonymous vs. authenticated callers receive different stock detail (yes/no vs. exact quantity), and prices are VAT-exclusive with price_vat_included=false and a separate vat_rate. It does not mention error behavior for an invalid or missing product_id, which keeps it from a 5.

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 the following sentences each add a distinct fact (auth model, field semantics/units, VAT, stock visibility). The middle sentence is long and packs several ideas (EAN, brand, pack unit, price_per_unit, weight_kg), but no sentence is 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?

There is no output schema, so the description carries the full burden of explaining return values — and it does, enumerating the key fields, their units, the VAT convention, and the caller-dependent stock field. Combined with the auth note, an agent has everything needed to call and interpret results.

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 0%, so the description would need to compensate, but it says nothing about product_id beyond the implicit context of "one product" — no format, source, or validity notes. The single parameter is largely self-evident from its name, so this is a gap but not a severe one.

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 first sentence gives a specific verb and resource — full detail of ONE product — and explicitly scopes it against the listing tools ("everything the listing tools return"). An agent can immediately tell this is the single-item detail fetch, not a search or list operation.

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?

Usage is implied rather than stated: "one product" and "everything the listing tools return" suggest this is for detail lookups after a list/search, and "Public — no authentication needed" is a useful precondition. However, it never explicitly says when to prefer this over search_products or how to obtain a valid product_id, leaving routing to inference.

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