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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial context beyond them: only connected sources are returned, one source failing does not suppress the others, and unmatched site_url yields scope.site_matched=false with a list of properties rather than silently substituting another site. This is exactly the kind of silent-fallback disclosure an agent needs.

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?

Front-loaded with the unified-overview claim and the funnel breakdown, then the failure and scoping rules. Dense and mostly earning its space, though the all-caps emphasis and the long site_url clause could be tightened.

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 complex multi-source aggregation tool with an output schema present, the description covers routing, partial-failure behavior, scope reporting, and account/property targeting. The only omission, `days`, is minor against an otherwise complete picture.

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 coverage the description must carry the burden, and it does for two of three parameters — customer_id (empty = selected account) and site_url (property targeting, format examples, and fallback semantics). The `days` parameter is never explained, leaving the default of 28 and the time-range meaning undocumented.

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 (aggregates) and resource (all connected Google sources as a funnel), and enumerates each source with its metrics. It is clearly distinguishable from sibling single-source tools like ga4_overview, gsc_performance, or youtube_overview.

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 establishes the core use case (one call for a cross-channel funnel), explains the multi-account targeting conditions for customer_id and site_url, and notes graceful partial-failure behavior. It does not, however, explicitly name alternative siblings (e.g. marketing_insights, performance_report) or state when NOT to use it.

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