compare_periods

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

Annotations already declare readOnly, idempotent, non-destructive, and open-world, so the safety profile is covered. The description adds that output is organized as daily values with percent changes, which is useful, but it says nothing about the deduplication/cross-source conflict resolution behavior that materially changes results.

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; the comparison semantics lead immediately. It is arguably too terse for a six-parameter analytical tool, but nothing is wasted.

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?

Six optional parameters, no output schema, and non-trivial deduplication logic leave the agent under-informed: the return shape (per-day rows? per-metric aggregates? ordering?) and the interaction between deduplicate and source_priority are unexplained. One sentence cannot cover this surface area.

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 only 50%: source, deduplicate, and source_priority are documented inline, while days (2-90 bound), timezone, and data_types carry no schema descriptions. The tool description mentions none of the parameters, so it does not compensate for the undocumented half — notably how timezone shifts day boundaries or what valid data_types are.

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 (compare) and resource scope (a recent period vs the immediately preceding one) with the metric form (daily numeric values and percent changes). This clearly separates it from plain retrieval siblings like get_metrics or get_daily_summary, though it never names get_trends, the closest analytical alternative.

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 'recent vs preceding period' framing implies the use case (period-over-period change analysis), but there is no explicit when-to-use guidance, no mention of when to prefer get_trends or get_daily_summary, and no prerequisites stated. Usage must be inferred rather than read.

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