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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is fully covered structurally. The description's added value is the returned metric set and the two time windows, which matters because there is no output schema. It does not clarify account/auth scope or define the jargon terms 'rescued' and 'ready', so the addition is modest rather than rich.

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?

A single sentence with zero filler, leading with the resource ('Totals across your mailboxes') and then the breakdown. Every clause carries information an agent would otherwise have to guess.

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 no-parameter, read-only, non-destructive aggregate tool with no output schema, the description covers the essentials: what is aggregated, over which windows, and which metrics come back. The remaining gap is scope (whose account/mailboxes) and the meaning of 'rescued'/'ready', which an agent calling this blind might misread.

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 tool takes zero parameters and the schema is an empty closed object, so there is nothing for the description to disambiguate. Baseline 4 applies; no parameter-level gaps exist.

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 the resource and scope precisely: aggregate totals across all your mailboxes, split into 'today' and 'last 7 days', with the exact metric names (sent, received, rescued, replied, active, ready). That is far more specific than a bare name restatement. It stops short of naming a sibling it is not (e.g. mailbox_activity, get_workspace_report), so an agent still has to infer the distinction from the sibling list.

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 'totals across your mailboxes' framing implies a dashboard/overview use case, and the presence of per-mailbox and per-workspace siblings (mailbox_activity, get_mailbox, get_workspace_report) makes the intended niche inferable. However, there is no explicit when-to-use or when-not-to-use statement, and no routing cue telling the agent to prefer this over those alternatives for an aggregate snapshot.

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