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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds real value beyond that by disclosing the output grain (one row per game) and the exact metric set, which matters because there is no output schema. It stops short of stating currency, timezone, or whether outstanding wishlists are a point-in-time snapshot.

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 compact sentences with the output grain and metrics front-loaded and no filler. The trailing sentence is thin but not wasteful. Slightly more structure (e.g. an explicit "compares" framing) would have improved it without adding length.

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-parameter read-only tool this is close to adequate: annotations carry safety and the description carries the output shape in lieu of an output schema. However, the metric list is incomplete relative to what a title comparison typically needs (no deltas, conversion rates, or units of currency), and the description never defines the comparative framing itself.

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%, including patterns and defaults for start_date and end_date, so the schema fully documents both parameters. The description's only nod to them is "for a period" and adds no format or edge-case meaning. Baseline 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?

"One row per game on the account for a period" plus a metric list tells the agent what comes back, so the purpose is inferable and not a tautology. But the description never states the action (comparing titles against each other) and never explicitly separates itself from siblings like get_sales or get_wishlist_activity, so the agent must guess how this differs from single-metric tools.

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?

"Useful for publishers with several titles" is an audience hint, not a when-to-use rule. There is no condition for choosing this over get_sales, get_wishlist_activity, or get_wishlist_breakdown, and no exclusions or prerequisites such as needing multiple titles on the account.

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