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

Annotations already carry readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds value beyond that: it discloses the returned field set and the storefront/locale defaults (country=us, lang=en), which tells the agent the result is locale-scoped rather than universal. It doesn't mention rate limits or whether optional vs. granted permissions differ, keeping it short of a 5.

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?

Front-loaded with what is returned and the purpose before the parameter restatements. It is efficient overall, though the ID and Country descriptions duplicate schema text verbatim, which is minor waste given 100% schema coverage.

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 and read-only/open-world annotations covering the safety profile, the description only needs to frame purpose, scope, and routing. It does all three, including the exact return fields, locale defaults, and the sibling tool to use for broader item data.

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 100%, so baseline is 3. The description largely restates the schema text for ID ('the 32-character extension id, e.g. cjpalhdlnbpafiamejdnhcphjbkeiagm') and Country ('Two-letter storefront country code, ISO-2'), adding the default values but no new semantics such as how country/lang affect the returned permission list.

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 permissions a Chrome Web Store extension declares in its manifest') and then enumerates the exact fields returned (permissions, optional_permissions, host_permissions, manifest_version, min_browser_version). It also names the sibling it is not (chromewebstore_item), so an agent can distinguish a manifest-permissions lookup from a general item details lookup without opening either 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?

Gives a clear use context ('Useful for security and supply-chain review') and explicitly routes to chromewebstore_item for item details. It lacks an explicit 'do not use this for X' exclusion, but the intended scenario and the alternative are both stated plainly.

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