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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), so the bar is lower. The description adds real value by disclosing the output shape — differing rows marked, cheapest/best-rated/best-choice highlights, Tryvon score — which is behavioral context the annotations cannot convey. It does not state whether results are cached or sorted.

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?

A single dense sentence that front-loads the action and scope, then lists the return dimensions. No filler, no repetition of the title.

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 carries the return-value burden and does so well, enumerating the compared attributes and highlight markers. The only gap is routing guidance against compare_prices and search_products, which the agent would need to select this tool confidently.

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% and the schema already documents product_keys with its source (productKey from search_products or top_products). The description's '2-4 different products' corroborates the bounds but adds no format or sourcing detail beyond the schema, so baseline 3 is appropriate.

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 (Compare) and resource (products) and enumerates exactly what the comparison surfaces: specifications, rating, lowest price/shop, shop count, delivery. It's clear what the tool does, but it never distinguishes itself from the sibling compare_prices, which an agent could plausibly confuse it with.

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 '2-4 different products' constraint implies usage but no explicit when-to-use or when-not guidance is given, and no alternative (compare_prices, search_products) is named. The agent must infer that this is the multi-attribute comparison path.

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