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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered by structured data. The description's only added behavioral fact is the per-request price ($0.012 USD), which is genuinely useful context annotations do not carry, but it says nothing about rate limits, aggregation behavior, or data freshness.

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?

The text is short and front-loaded with the heading, but most of its body is marketplace pricing boilerplate that does not help an agent select or invoke the tool. It is not bloated, but the useful-content-to-total-content ratio is poor.

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 not be explained, and annotations cover safety. However, for a tool with six optional query parameters and a confusingly similar sibling, the description provides no domain framing at all — no statement of what event metrics are, what time windows mean, or how this differs from get_agentmail_inbox_metrics.

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 description coverage is 100%, so all six parameters (start, end, period, limit, descending, event_types) are already documented in the schema. The description adds no additional meaning beyond that baseline, so a 3 is the correct floor.

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 is literally the title repeated: 'Query Metrics.' It restates the name rather than explaining what is being measured (delivery events? inbox activity?) or what resource the metrics belong to. With a near-identical sibling, get_agentmail_inbox_metrics, an agent cannot distinguish the two from this text.

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 when-to-use, when-not-to-use, or alternative-tool guidance anywhere in the description. The existence of get_agentmail_inbox_metrics makes this omission actively harmful, since nothing tells the agent which metrics endpoint to pick.

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