List Merchant Center accounts

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

Annotations declare readOnlyHint=true and destructiveHint=false, and the description aligns with these by describing a read-only listing operation. The description adds useful behavioral context by indicating it returns account types (standalone vs. MCA), which helps set expectations. It does not mention rate limits or auth requirements, but the annotations cover the safety profile adequately.

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?

The description is concise, consisting of two sentences that convey the essential purpose and usage without unnecessary detail. It is well-structured, front-loading the core function and then providing the key use case and a relevant distinction.

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?

Given the tool's simplicity (no parameters, read-only listing), the description is largely complete. It covers what the tool does, why it might be used (to discover merchant IDs), and a relevant detail (standalone vs. MCA). The output schema is not described, but for a list operation this is a minor omission, not critical for correct invocation.

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 has zero parameters, so schema coverage is 100%. According to the rubric, with high coverage, the baseline score is 3. The description adds no parameter-specific information (since there are none), so no additional credit is warranted.

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 clearly states the tool's purpose: listing Google Merchant Center accounts accessible to the connected user, and explicitly notes the distinction between standalone and MCA accounts. It also provides the primary use case (discovering merchant IDs for get_merchant_feed_health), making the purpose 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?

The description gives specific guidance on when to use this tool: 'Call first to discover merchant IDs for get_merchant_feed_health.' It also mentions the standalone vs. MCA distinction, which helps in selecting the appropriate account. However, it does not explicitly state when not to use it or alternative tools, though the guidance is sufficient for this simple list operation.

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