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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds behavioral content beyond that: results include product inventory and 'live' facets, and the response is paginated and requires a storefront-derived cid. It stops short of describing pagination limits or facet behavior, so it is strong but not exhaustive.

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 sentences, zero waste. The what-and-how is front-loaded, and the sibling routing is packed into the second sentence without redundancy.

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 an output schema present, return-value detail need not be repeated; the description still usefully notes inventory and live facets. It covers purpose, input keying, and alternatives. Minor omission: no note on pagination termination or page-size behavior, which matters for a paginated list tool.

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 100% with only three parameters, all documented in the schema (cid, page, brand with its documented values). The description reinforces that cid is a storefront URL value, but adds no syntax or format detail beyond the schema. Baseline 3 is appropriate when the schema carries the parameters.

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 (Fetch), a specific resource (a category), the multi-brand scope (Old Navy, Gap, Banana Republic, Athleta), and the keying mechanism (storefront `cid`). It also distinguishes itself from siblings by naming oldnavy_categories, oldnavy_search, and oldnavy_product. An agent can place this tool precisely without opening a schema.

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?

Explicitly routes the agent: use oldnavy_categories to discover IDs, oldnavy_search for keyword results, oldnavy_product for a single item. Both the when-to-use and the when-not-to-use (i.e., what the alternatives cover) are stated, leaving nothing to inference.

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