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's added behavioral detail is thin: the 'shelf the store renders' phrasing hints at a specific rendered block, but the defaults it lists (country=us, lang=en) are already in the schema. No auth, rate-limit, or result-shape context is added.

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?

Purpose is front-loaded in the first sentence, followed by defaults and parameter notes. Mostly efficient, though Country is effectively stated twice (in the defaults line and again as its own definition), a small 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?

An output schema exists, so return values need not be described, and annotations carry the read-only/open-world profile. The description supplies the required item-id format, locale defaults, and a sibling pointer, leaving nothing an agent needs to call it correctly.

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%, so the schema already documents ID, Lang, and Country. The description restates those same definitions (32-char id example, ISO-2 country, default en/us) without adding format rules, constraints, or enum-like guidance beyond what the schema provides. Baseline 3.

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: "Returns the related-items shelf the store renders on an item's detail page." That scoping lets an agent distinguish it from chromewebstore_item (details), chromewebstore_search (discovery), and chromewebstore_reviews 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?

Clearly establishes the input context (an existing item id) and explicitly routes to a sibling: "Use chromewebstore_item to retrieve Chrome Web Store item details." It gives context for when this tool applies but stops short of an explicit when-not or a named alternative that also returns related items.

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