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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds one genuine behavioral constraint — the two-to-eight item bound — but says nothing about what is returned or the effect of market/decision_id. Annotations lower the bar, so a 3 is appropriate.

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?

One tight sentence, front-loaded with the verb and scope, with the cardinality constraint in parentheses where it belongs. Nothing is wasted, though it is arguably too brief given the undocumented parameters.

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?

An output schema exists, so return values need not be described, and annotations cover the safety profile. Still, for a three-parameter tool with zero schema description coverage, the undefined market and decision_id parameters leave the definition only minimally adequate.

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 coverage is 0%, so the description must carry parameter meaning. It usefully clarifies that gtins accepts either GTINs or catalogue ids and constrains the count to two to eight, which the bare string-array schema does not convey. However, the market and decision_id parameters receive no explanation at all, leaving a real 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?

States a specific verb (compare) and resource (items, variants, pack sizes) with the mode of comparison (side by side). It is clear what the tool does, though it does not explicitly differentiate itself from siblings like get_item or get_price that also retrieve item 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?

The description implies the usage context (side-by-side comparison of two to eight items) which suggests when an agent would reach for it over a single-item lookup. However, it names no alternatives and gives no explicit when-not-to-use guidance or prerequisites.

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