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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds nothing beyond that: it does not say which metrics are returned, whether the two date parameters must be paired, or what the default time window is.

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 short clause with zero waste and the grouping dimension front-loaded, but it is terse to the point of under-specification rather than genuinely efficient communication.

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 seven parameters, no output schema, and no explanation of which performance metrics or response shape the caller receives, the description leaves an agent unable to predict results. The rich schema offsets this somewhat, but the metric content is never described anywhere.

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 examples and defaults for page, size, sort, fromMonth/toMonth, channels, and groupType, so the schema does the heavy lifting. The description itself contributes no parameter semantics at all; 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?

The description states a verb-less purpose, 'Performance metrics grouped by Country,' which is enough to infer a read-only reporting tool scoped to geographic breakdown. It does not distinguish itself from close siblings such as performance_metrics, account_level_stats, or deep_funnel_stats beyond the 'by Country' grouping.

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?

There is no guidance on when to pick this over performance_metrics or other reporting siblings, and no stated prerequisites (e.g., whether fromMonth/toMonth should be supplied only together). Usage is entirely inferred from the name and schema.

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