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

readOnlyHint=true already declares the safety profile, and 'Views' is consistent with a read. The description adds the aggregation shape (per day and per listing) that annotations cannot convey. It says nothing about scope defaults (all listings? active only?) or any data-freshness/timezone caveats.

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?

A single em-dash-delimited sentence that front-loads the metric list and closes with the time window. Every clause carries information and nothing is repeated from structured fields beyond the enum values.

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-only tool this is close to sufficient — metrics, granularity and window are all stated. Missing is whether the result aggregates across all of the caller's listings or requires a listing ID (there is no listing parameter), plus currency and timezone assumptions, which matter for an earnings field.

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%: the days enum with its 30-day default and the api_key fallback are both documented in the schema. The description restates the 7/30/90 window without adding format or behavior detail, so 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?

Names a specific resource (listing performance stats) and enumerates exactly what is returned: views, clicks, sales and earnings. The granularity clause (per day, per listing) sharpens it further. It doesn't contrast itself with the nearest siblings (get_sales, get_balance), so it stops short of a 5.

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 — an agent can infer this is the analytics/metrics tool and that get_sales or get_balance cover transaction-level or balance data, but the description never says so. There are no stated exclusions or prerequisite conditions.

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