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

Annotations already establish read-only, idempotent, non-destructive behavior, so the bar is lower. The description still adds real value beyond them: 'reads never trigger paid X work' (cost behavior), 'Unknown metrics are null' (null semantics), and coverage/freshness/versioning of the returned facts. That is meaningful behavioral context an agent could not get from annotations alone.

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?

Three short sentences with no padding, front-loading the read semantics and the kind requirement. Slightly dense jargon ('publication-cohort', 'versioned activity facts') costs it a point but nothing is wasted.

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?

An output schema exists, so return values need not be explained, and the description covers null handling and cost. However it omits what brandId/accountIds scope, how since/until are interpreted, and any differentiation from sibling report tools, leaving the definition adequate but incomplete for its complexity.

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 0%, so the description must compensate for all five parameters, and it only addresses 'kind' (loosely mapping activity/posts/audience). since, until, brandId, and accountIds receive no explanation of format, scoping, or interaction, which is a substantial gap for a 4-required-param tool.

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 names three fact families (versioned activity, publication-cohort, observed audience) that map onto the enum, so an agent can see roughly what is returned. But it never plainly says this is a performance report, and with many reporting siblings (get_analytics, get_channel_report, get_x_report, get_ad_performance) it does nothing to distinguish itself. Purpose is inferable but vague.

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?

'Choose kind explicitly' is the only usage instruction and it merely restates that a required enum must be supplied. There is no guidance on when to use this over the numerous other report tools, nor when-not to use it. Essentially no routing guidance.

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