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

Annotations already cover readOnly, idempotent, openWorld and non-destructive, so the safety profile is handled. The description still adds value beyond them: it discloses the authorization scope (accounts the user's connected Google account can see) and that ids are part of the response, both of which matter for chaining. It does not discuss pagination or listing behavior for very large account sets.

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 tightly packed sentences with zero filler. The resource and its scope come first, and the usage directive is placed after, which lets the agent read the identity before the instruction.

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 no output schema, the description should carry the return-shape burden, and it does at a high level by noting the accounts come with their ids. It is complete enough for a zero-input discovery tool, though it omits whether a not-connected state is returned and how large result sets behave.

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?

The tool takes zero parameters and schema coverage is 100%, so no parameter documentation is needed. The description correctly does not invent inputs and instead uses the space to describe the scope of the result set. Baseline 4 applies for a parameterless tool.

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 names the specific resource (the Google Merchant Center accounts visible to the connected Google account) and adds scope detail, clarifying that sub-accounts of a multi-client account are included and that ids are returned. It is not a bare tautology of the title. It stops short of naming its Merchant siblings (merchant_products, merchant_issues) to differentiate explicitly, but the resource is unambiguous.

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?

"Call this first for Shopping and free listing questions" gives explicit sequencing guidance, implying this discovery call precedes the other Merchant tools that need account ids. It establishes context well but does not name the downstream tools or state any exclusions, so it lands just below the top tier.

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