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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real context beyond them: the underlying daily aggregates, the 12-month retention window available on every plan, and org-local time-zone semantics. It doesn't discuss result ordering or pagination, but the added constraints are genuinely useful.

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 tight sentences with no waste: scope first, then the guiding use case, then the date/time-zone constraint. Every clause carries information an agent needs.

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 compensates by naming the return shape (event names with counts and share) and the retention horizon. The only unaddressed gap is what limit controls and the ordering of results.

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 80%, and the schema already explains from/to pairing, the days alternative, org defaulting, and org-local dates. The description's "Dates only, in the organization's time zone" largely restates that, and the undocumented limit parameter gets no help, so schema-coverage baseline of 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?

States a specific verb+resource (list event names) plus exactly what is returned (counts and share) and the data source (daily aggregates). This distinguishes it from siblings like event_stats and search_events, which operate on events rather than the org-wide name ranking.

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?

"Use it to learn what an organization sends before searching or computing stats" gives a clear when-to-use and implicitly routes away from search_events and event_stats. It stops short of naming those tools or stating exclusions, so it is strong but not exhaustive.

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