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

Annotations already declare readOnlyHint=true, destructiveHint=false and a closed-world scope, so safety is covered. The description adds the meaningful behavioral fact that results are pre-aggregated across three dimensions, but omits the notable point that no campaign parameter exists (scope is implicit), and says nothing about result volume or limits.

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?

Two sentences, front-loaded with the core capability. The second sentence partly restates the first ('multi-dimensional breakdown' → 'granular aggregate performance metrics broken down across') but does add the concrete dimension names and provider examples.

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?

With no output schema, the description must convey the return shape, and it only says 'aggregate metrics' without indicating fields, grouping granularity, or whether totals are included. For a reporting tool with a single time-window parameter, that leaves the agent unable to predict the payload.

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 single parameter has full schema description coverage ('7, 30 or 90 days', default 30), so the schema already carries the semantics. The description contributes nothing about the window — e.g. whether it applies to send date or reply date — so the baseline 3 applies.

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 concrete output and its dimensions (provider, mailbox, sentiment) rather than restating the name, so an agent knows this is an aggregate reporting tool rather than a single-campaign fetch. It does not explicitly name how it differs from the very similar siblings get_campaign_stats and get_overview, leaving differentiation partly inferential.

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?

There is no guidance on when to choose this over get_campaign_stats or get_overview, which are the closest siblings and cover overlapping analytics territory. The description also never states that the tool is account-wide (it takes no campaign identifier), which is exactly the kind of scoping rule that would drive selection.

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