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

The annotations only declare readOnlyHint, openWorldHint, and destructiveHint. The description adds substantial behavioral nuance beyond that: results are account-summary-qualified, not unique orders, cannot be allocated to ASIN/SKU, legacy non-adopted scopes keep 'Orders' labels, explicit data gaps must be preserved, and trends should only be reported when returned. This is rich, non-obvious behavior that helps the agent use results correctly.

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 long and dense, but every sentence earns its place by conveying a distinct constraint or use case. It is front-loaded with the core purpose and then layers caveats and usage intent. Slightly better formatting (e.g., bullets) could improve scannability, but it is not bloated or redundant.

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 must explain what the tool returns, and it does: sales, units, order items, with the caveat that they are not unique orders. It also covers data-gap handling and trend reporting. For a single-optional-parameter read-only tool with these complexities, the description leaves no critical operational gap.

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?

There is only one parameter, days, and the schema already describes it thoroughly with type, default, minimum, maximum, and meaning ('Trailing completed-marketplace-day window'). The description repeats the range in prose but adds no new parameter-level semantics. With 100% 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 opens with a specific verb and resource: 'SALES / REVENUE for 1–30 completed exact-marketplace days.' It enumerates the return metrics (sales, units, order items) and explicitly distinguishes itself from order-level tools by noting it returns 'not unique orders.' This lets an agent differentiate it from siblings like get_orders_summary without deep schema inspection.

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 provides explicit when-to-use guidance: 'Use for "sales", "revenue", "how much did I sell", "sales last 7 days".' It also provides strong when-not guidance by warning against allocating to ASIN/SKU or using for margin/ACoS. However, it does not name a specific alternative tool to route to for those excluded use cases, so it falls short of the top score that requires naming alternatives.

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