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

With readOnlyHint=true and openWorldHint=false already in annotations, the description adds quota-status disclosure: it tells the agent to communicate approaching/grace/blocked quota and to include the upgrade link supplied in the result. This is useful behavioral context beyond the structured annotation. It also implies a comparative vs-previous-period behavior. It could have disclosed pagination or exact return-field details, but the output schema exists, so a 4 is appropriate.

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?

The description is compact and front-loaded: the first sentence delivers the core content list, the second adds period semantics, the third gives actionable quota guidance. Every sentence earns its place, and the most selection-relevant information appears 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?

For a two-parameter read-only tool with an output schema present, the description covers what the tool returns, the key parameter behavior, and a special quota-notification requirement. It doesn't name sibling alternatives, but sibling names are visible in context. Minor gap: no explicit statement about what happens if the account has multiple sites and site is omitted. Still, completeness is high.

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%, so the schema fully documents 'site' and 'period'. The description reinforces the relative-period semantics ('period: relative like...') and adds the default-value note, but it does not deeply expand beyond the schema. Baseline 3 is correct because the schema already carries the parameter meaning.

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 opens with a vivid, specific summary: 'visitor/pageview totals vs the previous period, top pages, top referrers, and a per-day series.' That names a clear verb+resource and distinguishes this overview tool from analytical siblings like funnel, journeys, what_changed, query. The title 'Site overview' is expanded into actual content dimensions, so the purpose 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?

The description explains the default period ('7d'), that period is relative, and that site can be omitted for single-site accounts or read from the script tag in tracked projects. It also explicitly singles out quota-status behavior and when to mention it ('approaching... while there is headroom'). It does not explicitly name alternatives or exclusion conditions versus siblings, but the context is clear enough for an agent to select it for high-level traffic overview.

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