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

Goes well beyond the readOnly/idempotent annotations: it discloses the returned field set, states that results preserve requested order, that each entry carries a status and complete flag that must be inspected, and that unavailable products are not substituted. The explicit anti-hallucination instruction ("never invent doses, serving counts or price per serving") is exactly the kind of failure-mode guidance an agent needs.

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 in the first sentence, followed by return shape and then guardrails, in a logical order. It is dense and largely waste-free, though the telegraphic later sentences ("Preserve requested order; inspect each status and complete flag") read as terse fragments rather than a structured set of rules.

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 usefully enumerates return fields, and it covers partial-result and ordering semantics for a multi-ID lookup. Missing only the provenance of region_id and any error/no-match behavior for the overall call.

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 carries the burden; it does add that IDs must be distinct and that all products are resolved against a single region. It does not explain what region_id is, where to obtain one (delivery_regions), or what happens on malformed/unknown IDs, so the coverage gap is only partially closed.

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 2 to 5 distinct products") plus the scope (one selected Russian delivery region) and what is returned (RUB prices, brand, form, ingredients, manufacturer usage). Clearly separable from siblings such as product_details (single item), product_analogs (substitution) and products_search (discovery).

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?

The 2–5 product, single-region framing makes the intended use case unmistakable, and "No medical equivalence or treatment advice" plus "no serving counts" draw boundaries. It never explicitly names a sibling alternative or says when to prefer product_details/product_analogs over this, so the routing is implied rather than spelled out.

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