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

Annotations already cover the safety profile (readOnlyHint, idempotentHint). The description adds one genuinely behavioral fact: fewer than 2 or more than 5 items returns an error. Beyond that, it does not say what dimensions are returned or whether comparisons are cached/derived, so value beyond annotations is modest.

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?

Three short sentences with no filler, and the core purpose is front-loaded. The inline "asins:" labeling is slightly awkward formatting but still scannable and efficient.

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?

For a one-parameter tool this is close to complete on the input side. However, a comparison tool's main unknown for an agent is what the comparison actually contains (which dimensions), and the description only gestures at "dimensions" without any listing or return-shape hint.

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% and the schema is untyped (items: {}), so the description must do the work. It does: ASIN count range, length restriction (10-char alphanumeric), a concrete example, and the out-of-range error behavior. Only the item type declaration in the schema remains unspecified.

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 two to five products side-by-side across dimensions." It is clearly distinct from single-product siblings like get_product or search_products, though it never names those alternatives explicitly.

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?

It gives a hard usage constraint (2-5 ASINs, error otherwise but that only defines valid input, not when to choose this tool over calling get_product repeatedly or search_products. Usage context is implied by the verb "compare" rather than stated.

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