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

Annotations already declare readOnly=true, idempotent=true and openWorld=false, so the safety profile is covered. The description adds real value beyond that: the explicit bound of 2-6 products and the disclosure that results include full records plus a field-by-field table keyed by slug. It does not cover failure modes (e.g., unknown slug handling), which keeps it out of 5 territory.

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?

Two tight sentences, zero filler, with the comparison scope front-loaded and the return shape second. Every clause carries information an agent can act on.

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 explained, yet the description still summarizes the response shape. Combined with annotations covering safety and a single fully documented parameter, nothing an agent needs to invoke this correctly is missing.

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?

Only one parameter, fully described in the schema (including minItems 2 / maxItems 6), so schema coverage is effectively 100%. The description's '2 to 6' merely restates the schema constraint and adds no semantics beyond it. 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?

Specific verb (compare / side by side) plus resource (products) and an explicit enumeration of the comparison dimensions: pricing, free tier, API, MCP, SDK, open source. It implicitly separates itself from single-record siblings like get_product, but never names find_alternatives or search_products, so it falls short of full sibling differentiation.

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 to 6 products' framing implies the usage context (batch comparison of a short candidate list) but there is no explicit when-to-use, when-not-to-use, or routing to alternatives such as find_alternatives for discovery vs. this tool for head-to-head comparison. Usage is inferable but not stated.

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