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

Annotations already cover the safety profile (readOnly, non-destructive, open-world), so the bar is lower. The description still adds real behavioral detail not in those annotations: the weekday indexing convention (Monday is 0) and the one-day range requirement for minute granularity.

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: the breakdown modes first, then the value proposition, then the endpoints. Nothing is padded and the most decision-relevant 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?

With no output schema, the description carries the burden of describing returns, yet it never indicates the shape of the result (e.g., a list of hour/minute/weekday buckets with visitor counts). The core invocation semantics are covered, but return-value context is missing for a 29-parameter statistics tool.

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%, so baseline is 3, but the description adds meaning beyond the schema by documenting the weekday index origin (Monday is 0) and restating the by-mode semantics in the context of the API paths. It does not touch the 20+ optional filters, which the schema already documents thoroughly.

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 and resource (visitor counts broken down by hour/minute/weekday-hour) and pins down the semantic dimension, which separates it from pirsch_get_visitors_time_series and pirsch_get_duration. The API endpoint list reinforces exactly which resource is queried.

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?

It gives one usage constraint (minute breakdown requires from and to on the same day) and a motive ('shows when traffic peaks'), which implies the use case. However, no alternative is named and no when-not condition is stated, so an agent must infer when this beats the time-series or totals siblings.

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