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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: net contribution is computed after Amazon fees, product cost, and ads, and a `narrative` field carries the interpretive answer — information an agent cannot get from the annotations or schema. It omits caveats such as attribution windows or what happens when ad data is missing.

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 sentences with essentially no filler, and the resource definition is front-loaded before the output-reading instruction. The metric list is dense domain jargon, but every clause carries information rather than padding.

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 two-optional-parameter read tool with no output schema, the description supplies the key output vocabulary (spend, ad sales, ACoS, break-even, net contribution, narrative) so the agent knows what comes back. It leaves the time-window behavior and empty/no-ad-spend cases unaddressed, which is a modest gap given how simple the input surface is.

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%, with both `days` (window and default) and `marketplace_id` (single-marketplace inference) fully documented in the schema. The description adds no syntax or meaning beyond the schema, so the baseline of 3 applies.

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 resource precisely — advertising metrics broken down per advertised SKU — and lists the concrete outputs (spend, ad sales, ACoS, break-even, net contribution), which clearly separates it from campaign-, target-, or search-term-level siblings. It never states an explicit verb or naming contrast with the closest siblings (get_profit_by_sku, get_ads_arm_economics), so an agent must infer the distinction rather than read it.

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?

Usage is only implied: the per-SKU advertising framing plus 'Read its `narrative` as the answer' suggests when to reach for this tool and how to consume the output. There is no statement of when to prefer it over get_profit_by_sku or get_ads_overview, no exclusions, and no prerequisites (e.g., whether Amazon Ads must be connected).

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