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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds one genuine nuance beyond them: the sent/delivered/failed/received figures are windowed over the last N days while 'waiting now' is a live snapshot — useful, but return shape, aggregation scope (workspace-wide vs per-device) and any latency are left unstated.

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?

One front-loaded sentence with no filler, and the list of metrics plus the window arrives immediately. The interrogative phrasing is slightly informal for a tool definition but wastes nothing.

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 values need no explanation, and the annotations carry the safety profile; for a one-parameter read-only stats tool this covers what an agent needs to call it. Remaining gaps — aggregation scope and default window — are minor rather than blocking.

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 'days' parameter is undocumented in the schema (0% coverage), and the description only partially compensates by saying the counts span 'the last N days.' It never states the 30-day default or the 1–90 range, so constraints must be read from the schema.

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 names the exact metrics produced (sent, delivered, failed, received, waiting), which is a specific resource plus a set of countable outputs, and it is clearly distinct from message-level siblings like list_messages or get_message. It doesn't restate the name but also doesn't frame the tool with an explicit verb, so it falls just short of a model example.

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?

Usage is only implied: an agent can infer 'call this when you want aggregate numbers rather than message records,' and 'how many are waiting now' hints at a live-queue check. No alternative tool is named and no when-not condition is stated.

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