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 genuinely useful behavior beyond that: results come from daily aggregates with 12 months of history on every plan, only dates are accepted (no finer granularity), and dates are interpreted in the organization's time zone. These are real constraints an agent could not read off 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?

Two dense sentences, front-loaded with the operation and its outputs before the retention and timezone caveats. Every clause carries information, though the sentence fragment 'From daily aggregates (12 months on every plan)' reads awkwardly and takes a beat to parse.

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 five parameters and no output schema, the description carries the burden of conveying the return shape, and it does so by naming the four breakdowns (per day, per level, total, versus previous period). The org/event_name scoping and the days-vs-from/to alternatives are covered by the schema. Only the exact structure of the returned figures remains unspecified, which is a minor gap.

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 both the from/to pairing and the days-as-alternative semantics are already documented in the schema. The description reinforces the date-only and org-timezone framing but adds no format or precedence detail beyond what the schema provides; 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 specific resource and operation — event counts over a calendar-day range — and enumerates the aggregations returned (per day, per level, total, previous period) plus the scope (whole org or a single event name). This is far more specific than the title 'Event statistics'. It does not, however, differentiate itself from similarly-named siblings such as get_usage, leaving the agent to infer the boundary.

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?

Usage is implied rather than stated: the retention note ('12 months on every plan') and the 'dates only, in the organization's time zone' constraint tell the agent what data is reachable, but there is no explicit when-to-use or when-not-to-use guidance and no alternative tool is named. An agent can infer the intended context but gets no routing help.

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