mailkite_get_usage

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

The readOnlyHint annotation already signals no side effects, and the description adds value by disclosing the authentication requirement ('management session token') and the behavioral consequence of overage state gating sending. This goes beyond the structured annotation.

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?

Three short sentences deliver all essential information: what is measured, how it is used, and what access is required. No fluff, front-loaded with the core purpose.

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 parameterless, read-only query, the description is complete: it defines the output fields, the use case, and the authentication requirement. It could optionally specify response formatting, but that is not essential for correct invocation.

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 narrativeschema covers everything; there is nothing for the description to clarify. The description appropriately focuses on the return semantics instead.

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 clearly states the tool returns billing-period usage metrics: emails used versus the included bucket, AI actions, and the overage state that gates sending. It names the specific resource and differentiates this read-only monitoring tool from the many send/management siblings.

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 provides a clear use case—powering quota meters in dashboards and integrations—and an implicit context of checking sending capacity via the overage state. It doesn't explicitly exclude alternatives, but no direct sibling competes with this function.

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