investigate_change

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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds real behavioral context beyond them: what the output contains (equal-duration comparison, additive source/device/browser/path changes, coverage, timeline notes, caveats, next checks) and the important epistemic caveat that it 'describes associations, not causes.'

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, front-loaded with the core action and no filler. Slightly jargon-dense phrasing ('additive source/device/browser/path changes') partly offsets the otherwise efficient structure.

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?

An output schema exists so return-value detail is optional, and the description still usefully previews return contents. With 6 parameters at 0% schema coverage, the undocumented filters argument is the main remaining hole; otherwise the agent has enough to call it correctly.

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 0%, so the description must compensate, and it does for metric, event_name, and the date_from/date_to vs days relationship. It says nothing about the filters parameter (field/value structure, limit of 30 values) or how days defaults when dates are supplied, leaving meaningful gaps.

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+resource ('Investigate changes in pageviews, events, or event_count') and scopes which metrics are supported plus the event_name prerequisite. An agent can distinguish it from siblings like compare or breakdown, though it never names an alternative explicitly.

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?

Gives conditional guidance for one parameter set ('Use date_from/date_to together... otherwise days determines it'), which is useful. However there is no when-to-use versus when-not, and no routing to alternatives such as compare or detect_anomalies for related questions.

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