Compare Pirsch periods

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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile is covered. The description adds useful non-obvious context — that the tool produces both aggregate totals and a visitor series, and that periods can be supplied two different ways — but it does not disclose how the comparison is presented (deltas vs side-by-side) or how named and explicit periods interact.

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 15-word sentence that front-loads the verb and resource and compresses both period-specification modes into one phrase. There is no filler, redundancy, or repetition of schema or annotation content.

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?

While the output schema and safety annotations cover return values and side-effect profile, the tool is highly complex (47 parameters, 0 required, 0% schema coverage) and the one-sentence description covers only the core concept. An agent still cannot determine which parameters form the primary versus comparison period pair, how 'period' interacts with explicit date ranges, or what most optional parameters mean, so the description is insufficient for confident invocation.

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?

With 0% schema description coverage across 47 parameters, the description must carry semantic weight. It contributes the central concept that two periods are involved and can be expressed by name (mapping to 'period') or explicitly (mapping to from/to plus compareFrom/compareTo). Yet it never names these parameters or clarifies the remaining filter/dimension parameters, leaving the agent to infer their roles from their names alone.

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 verb ('Compare'), a concrete resource ('Pirsch totals and visitor series'), and a scope ('a named or explicitly supplied pair of periods'), going well beyond the title. It also implicitly differentiates from siblings like pirsch_list_domains (listing), pirsch_query_statistics (single-scope querying), and pirsch_list_filter_options (enumerating options), since comparison is a distinct operation.

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 use case is implied rather than stated: invoke this tool when a two-period comparison is needed, and choose between a 'named' period or an explicit date pair. However, it never explicitly routes away from pirsch_query_statistics for single-period needs or states when not to use this tool, leaving the agent to infer the decision boundary.

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