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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so safety is covered. The description adds real value by disclosing that the returned content differs fundamentally by mode (per-event breakdown vs cross-event streaks/retention/growth), which the annotations cannot convey.

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 sentences, front-loaded with the common single-event case before the fallback aggregate mode. The field lists are dense but each item maps to a distinct insight, so little 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?

With no output schema, the description must describe the return content, and it does so thoroughly for both modes. It omits any note on response shape/pagination, but for a read-only insights call that gap is minor.

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% – both apiKey and eventId are documented in the schema, including the 'leave out for all events' behavior. The description restates the eventId semantics without adding syntax or format detail, so baseline 3 is appropriate.

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 (event attendance insights) and enumerates exactly what it computes: counts, no-show rate, geography, first-timers vs returning, orgs, registrations over time. This clearly separates it from list_event_registrations (raw rows) and list_events in the sibling set.

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?

Explicitly defines the two operating modes: single-event when eventId is given, and cross-event aggregate insights when omitted. That is clear usage context, though it never names the sibling tools (e.g. list_event_registrations) an agent might otherwise reach for.

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