compare_periods

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

The annotations already indicate readOnlyHint=true and idempotentHint=true, so safety and idempotence are covered. The description adds useful behavior beyond the annotations: it excludes the event day from both sides when anchor is used, and it says the tool reports how many days it excluded when excludeTravelDays is set. That gives an agent a solid model of aggressive time and side effects.

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 cosrne and front-loaded: it immediately states the operation and result, then gives the two input patterns. No sentence is wasted; it delivers the vervalue in two sentences. The long second sentence with parentheticals adds a little cost but still earns its place.

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?

Given no output schema, the description does summarize the output shape: each aggregate plus change/percent change and, when excluding travel days, the number excluded. Combined with sibling semantics and annotation safety profile, this is reasonably complete, but it could drive lightly about metric values and required period constraints for the min agent.

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?

The overall schema describes some parameters, but coverage in the schema is only 40%; the description partially compensates by explaining the anchor/periodA/periodB relationship and the 'exclude the event day' nuance. However, it doesn't describe metric options or the exact date range semantics for periodA/periodB (boundary inclusivity, same length requirement). It thus adds meaningful but incomplete semantics over the schema.

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 operation: 'Compare a metric between two arbitrary date periods (A vs B)' and describes the result as each aggregate plus raw change and percent change. It is distinct: it compares period aggregates, and the sibling list contains no other true period-to-period comparison tool, so an agent can tell when to choose this tool.

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 gives clear context for use: explicit periodA/periodB for arbitrary periods, or anchor-based 'before/after' comparisons around a registered event. It does not mention alternatives among siblings or explicitly say when not to use this tool, so it stops just short of a 5.

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