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

Annotations already declare readOnly/idempotent/non-destructive, so the bar is lower; the description nonetheless adds material context the annotations cannot: the data comes from Amazon's own Sponsored Display report and includes view-through purchases under Amazon's attribution, which changes how the numbers should be read. It stops short of describing refresh cadence or latency, so not a 5.

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?

Front-loaded with the metric inventory so the agent knows what it gets before the caveats, and every clause carries information. The opening sentence is dense and could be split, but nothing is filler.

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?

No output schema exists, yet the description enumerates the returned metrics and their grain (per campaign), names the data source, and supplies the attribution caveat needed to interpret results correctly. With zero required parameters and full schema coverage, nothing an agent needs to call or read this tool is missing.

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 coverage is 100% and all three parameters (days range/default, account seller id, marketplace inference) are documented in the schema itself. The description only reinforces the 'window' concept and adds no syntax, units, or constraint detail beyond it, so the baseline 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?

States a specific resource (Sponsored Display campaigns) and enumerates the exact metrics returned: spend, sales, ACoS, orders, detail page views, new-to-brand orders, at per-campaign grain over a window. It also distinguishes itself from Sponsored Products attribution, so an agent can separate it from get_sponsored_brands and the general get_ads_* siblings.

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?

Gives concrete triggering questions ('how are my display ads doing', 'is retargeting worth it') that map directly to user intent. It flags an interpretation caveat versus Sponsored Products but does not explicitly name an alternative tool to use instead for cross-channel comparisons.

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