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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description adds meaningful context beyond them: it is FREE during validation, requires no key/credits/wallet, and is subject to existing source and input limits. This pricing/auth context is exactly the kind of non-annotation behavior an agent needs.

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?

Four short sentences with the core purpose front-loaded. The free/limit notes are slightly repetitive ('FREE during validation' and 'No key, credits or wallet' overlap), but nothing is padded or wasted.

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 read-only comparison tool with an output schema present, the description covers purpose, cost/auth model, and limits adequately, so return values need not be explained. Only the absence of usage routing to alternatives leaves a minor gap.

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 67%, and the description usefully maps the semantics of the two nested 'input' keys (requested = requested product attributes, offered = offered variant). The legacy params are documented in the schema itself as ignored, so the description's added value over the schema is modest but real.

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?

The description states a specific verb ('Compare') and resource ('requested product attributes' vs 'an offered variant') and names the concrete output ('missing or mismatched fields'). It is clear and self-contained, though it does not differentiate itself from any sibling tool by name.

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 the condition 'during validation' and notes free access, but there is no explicit when-to-use vs when-not, and no alternative sibling is referenced (e.g., commerce_feed_page_compare or commerce_pack_size_normalize). Usage is only implied.

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