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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds genuinely useful behavioural detail beyond that: results are count-ranked and include per-day totals for both the current and preceding period, which is exactly the return-shape context an agent needs given there is no output schema.

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 no filler; the rationale clause 'so a rise or fall is visible' justifies the comparison behaviour rather than padding. It is slightly run-on but every clause carries information.

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 does useful work describing the ranked plus two-period per-day return content, and defaults are covered in the schema. But for a tool sitting next to search_events it omits the routing information that would make selection unambiguous, leaving a real 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%, with each of days, limit and property fully documented in the schema, so the description is not required to compensate. It adds nothing about parameter meaning or interaction (e.g. how days relates to the comparison period), making the baseline 3 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?

The description gives a specific resource (events) and an explicit ordering (ranked by count over a period), plus the per-day comparison framing. It is clear what the tool returns, but it never distinguishes itself from the sibling search_events or list_pages, so an agent must guess which of the two event tools to pick.

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?

There is no when-to-use guidance and no mention of alternatives such as search_events, which is the obvious near-neighbour. The phrase 'ranked by count' hints at a top-N summary use case, but the agent is left to infer that this is the non-search, aggregate view.

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