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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known. The description adds that a valid timeframe must be specified and defaults to MONTH_TO_DATE if ambiguous, and it enumerates the metric categories returned. These details go beyond the annotations by describing query scoping and output content.

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?

The description is well-structured with clear headings (USE FOR, NOT FOR, TIMEFRAMES, METRICS, REQUIRED). Each section delivers useful information without redundancy, and the one-line summary is front-loaded. No wasted words.

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 annotations covering the read-only safety profile and the schema detailing all four parameters, the description completes the picture by listing available metrics and valid timeframes, and by noting the mandatory timeframe requirement. It does not mention pagination behavior, but the schema's page/size parameters already address that. For a stats-read tool with no output schema, this is sufficiently complete.

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 the baseline is 3. The description repeats the timeframe enum and default from the schema without adding new parameter-level meaning. The METRICS list implicitly relates to sort fields, but this is not explicit, so it does not raise the score.

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 clearly identifies the tool as providing website visitor engagement metrics, listing specific data types (session data, page views, visitor behavior analytics). The NOT FOR section explicitly distinguishes it from sibling tools like experiment_performance_stats and demographic_country_stats, so an agent can easily tell it apart.

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?

The USE FOR block enumerates concrete use cases (website traffic/engagement, conversion funnel, engagement trends) and the NOT FOR block names excluded scenarios with exact sibling tool references. This gives explicit when-to-use and when-not-to-use guidance with alternatives, leaving nothing to inference.

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