investigate_change

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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds meaningful context beyond annotations: the equal-duration comparison model, the additive breakdown dimensions, and the explicit "associations, not causes" caveat that frames how results should be interpreted.

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?

Four sentences, front-loaded with purpose and return scope, then the windowing rule. Efficient with little waste, though the return-content sentence partially overlaps the existing output schema.

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 investigative tool with an output schema already covering return values, the description supplies the key framing (what it compares, causal limitation, window logic). Missing only explicit sibling routing, which is not strictly required.

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 0%, so parameters are undocumented structurally, and the description only compensates partially — it clarifies event_name requirement for event_count and the date_from/date_to vs days interaction. Metric values, filter shapes, and date formats remain unexplained.

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 ("Investigate") and resource ("changes in pageviews, events, or event_count"), with a conditional qualifier for event_count. This distinguishes it from siblings like detect_anomalies and compare without opening their schemas.

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 explains the date_from/date_to vs days window logic, which is real usage guidance, but never states when to choose this tool over detect_anomalies, compare, or query_metrics, nor any exclusions. Usage is implied rather than routed.

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