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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the 'bounded' qualifier, which hints at limits, and the grouping behavior. It does not disclose details like default limit of 100 rows or that metrics default to visitors/pageviews, but with strong annotations the bar is lower; the description adds some value without contradicting 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?

Two sentences with no filler. The first sentence states the core behavior and grouping options; the second explains the use case. Every word earns its place and the key information is front-loaded.

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 read-only, idempotent time-series tool with 100% schema coverage, the description is nearly complete. It explains the grouping intervals and the analytical question it answers. It could mention the default limit or default metrics, but those are already in the schema, and the annotations cover the safety profile. Minor gap: no explicit mention of the two-item ISO date array option, but the schema covers that.

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 already documents all 7 parameters. The description adds the conceptual framing of 'bounded metrics grouped by time bucket' but does not add syntax or format details beyond the schema. Baseline 3 is appropriate when the schema carries the parameter documentation burden.

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 states a specific verb ('Return') and resource ('bounded Plausible metrics grouped by day, week, month, or hour'), and adds the question it answers ('when traffic, engagement, conversions, or revenue changed during a period'). It is clear about the time-series nature, which distinguishes it from sibling tools like plausible_breakdown and plausible_overview, though it does not explicitly name those siblings.

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 implies usage for time-bucketed trend analysis ('Answers when...changed during a period'), which gives an agent context for when to choose it. However, it does not explicitly state when not to use it or name alternatives such as plausible_breakdown for dimension-based breakdowns or plausible_overview for summary metrics. The guidance is adequate but not explicit.

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