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

Annotations already declare readOnlyHint=true and destructiveHint=false, so 'Read-only' earns no credit. What does add value is the ranking-fairness policy ('never by commission') and the affiliate-parameter policy ('only after approval'), which are real behavioral constraints not expressible in the annotation set. It stops short of covering failure modes such as invalid IDs or unsupported region combinations.

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 paragraph, front-loaded with the purpose and ranking rule before the telegraphic Inputs/Returns breakdown. Every clause carries information, though the Returns sentence is a long run-on that could be split for faster scanning.

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 correctly compensates by enumerating the returned fields (price, price per serving, testing, dose, caffeine, store URL). All three parameters are described and the safety profile is covered by annotations. The missing piece is guidance on how ties or default criteria are handled.

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 must carry the parameter burden — and it does, restating the 1–5 product_ids bound, the EU/US region values, and the four criteria names. It does not clarify whether omitted criteria means a default ranking or no ranking, which is the one real semantic gap.

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?

Opens with a specific verb, resource and scope: rank up to 5 products by stated criteria, with an explicit ranking policy (never by commission). The name/title 'compare products' is vague on its own, but the description immediately disambiguates it from plan_stack and shopping_list by framing it as a criteria-ranked comparison that returns row data.

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 by the input list and the 'never by commission' ranking rule, but there is no explicit statement of when to choose this over plan_stack or shopping_list, nor any prerequisite or exclusion. An agent can infer the context (product comparison across regions) but must reason about sibling selection on its own.

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