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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds minimal context beyond that: 'Current' signals this is not a staged or hypothetical view, and 'coverage summary' hints at aggregation or completeness. It does not explain what 'coverage' means or what happens when the token has multiple seller connections, but for a read-only tool these are moderate gaps.

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 one concise sentence with no filler and front-loads the key resource and scope. It earns its place, though it is terse enough that 'coverage summary' could have been clarified without much length. Overall it is well structured and easy to scan.

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?

For a tool with one optional parameter and read-only annotations, the description is mostly adequate, but the absence of an output schema makes the vague 'coverage summary' more significant. An agent cannot tell whether the tool returns a detailed line-item list, a summary object, or both. It also does not clarify how seller filtering behaves when multiple connections exist, though the schema partially handles that.

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%, and the single optional seller_connection_id is already documented well in the schema, including the conditional requirement. The tool description adds no parameter-level meaning beyond pointing at COGS. With full schema coverage, the baseline of 3 is appropriate.

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 states the resource clearly: per-SKU landed costs (COGS), and adds scope via 'Current' and 'coverage summary'. It is easy to tell this is a read-style COGS tool rather than a staged update, and the readOnlyHint annotation reinforces that. However, it does not use an explicit verb like 'retrieves' or 'lists', and 'coverage summary' is slightly vague.

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 no explicit guidance about when to use this tool versus alternatives such as stage_cogs_update or product_fee_preview. The word 'Current' implies it is for viewing existing COGS rather than updating them, but no exclusions or alternative routing are stated. An agent must infer the usage context from the name and annotations.

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