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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered; the description adds genuinely new behavioral facts — the 90-day event-count window, that the country filter only works from a specific date, and that results reflect plan-level limits. It stops short of saying whether the call consumes request quota or how fresh the counts are.

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?

A single front-loaded sentence with a colon-delimited list of outputs — no filler, no restatement of the title, and the most useful framing (key scope) comes first.

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 zero parameters, an available output schema for the return shape, and annotations covering the safety profile, the description supplies exactly the extra context needed: what dimensions of coverage and which limits it reports, plus the temporal constraints on the data.

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?

There are zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 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 names a specific verb ('Show') and an exact resource scope: what this API key can access. It enumerates the concrete payload (countries with event counts, earliest event, country-filter start date, plan limits), which makes it unmistakably distinct from event-listing siblings like get_event, event_stats and search_events.

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 only implied: an agent can infer this is a discovery/introspection call to make before querying events, but the description never says when to call it, when not to, or how it relates to alternatives. No prerequisites or follow-up routing are stated.

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