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

Annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, openWorldHint=false). The description adds one genuinely useful behavioral trait beyond them: results are ranked by count. It says nothing about response shape, whether zero-result domains return empty, or how 'custom' events are defined, so it is minor value on top of 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?

A single front-loaded sentence with no filler and no repetition of schema or annotation content. It is efficient, though arguably too terse to carry everything this tool 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?

For a simple, all-optional three-parameter read tool with full schema coverage and annotation-backed safety, the description is minimally adequate. However, there is no output schema, so the description could reasonably have said what an event row contains; it only notes the ordering, leaving return shape unexplained.

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 coverage is 100% with documented defaults, ranges, and the max 90d constraint, so the schema does the heavy lifting and baseline 3 applies. The description adds no parameter meaning of its own.

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 resource (custom events from measuremysite.track) and its ordering (ranked by count), so an agent can tell this apart from generic listing siblings like top_pages or query_visits. It does not explicitly contrast itself with those siblings, but the scope is unambiguous.

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, no alternates named, and no prerequisites stated. The purpose implies a listing use case, but nothing tells the agent when to pick this over top_pages, query_visits, or the other analytics siblings.

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