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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered and the bar is lower. The description adds useful domain context about accepted channels and timeframe formats, but says nothing about pagination behavior or return shape. Adequate but not rich beyond the annotations.

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 one-line purpose, then consistently labeled sections (USE FOR, NOT FOR, CHANNELS, TIMEFRAME, METRICS). The METRICS list is long but directly serves the sort parameter, so each block earns its place.

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 7-parameter read-only analytics tool with no output schema, the description covers routing, channels, timeframe formats, and metric vocabulary. The remaining gap is the return structure (one row per country, metric fields), which the absence of an output schema leaves undocumented.

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%, so baseline is 3. The description goes beyond the schema by documenting natural-language timeframe ranges ("last two months", "last 20 days") and enumerating the valid metric names, which add meaning to the fromMonth/toMonth and sort parameters respectively.

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 and grouping: "Performance metrics grouped by Country." The USE FOR / NOT FOR blocks explicitly name the siblings it is not (account_level_stats, experiment_performance_stats, performance_metrics), so an agent can disambiguate without opening other schemas.

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?

Provides an explicit USE FOR list (country/geography, geographic comparison, regional ROI) and a NOT FOR list that routes to three named alternative tools by scope (account, campaign, ingredient). The when/when-not/alternative pattern is fully covered.

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