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

Discloses the 24-hour expiry and the returned fields (email address, creation time, expiry). Annotations already indicate non-read-only and non-idempotent behavior, so the description adds meaningful lifecycle context beyond annotations.

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 that front-load the action and outcome, with no unnecessary words. Every sentence earns its place.

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 simple zero-parameter creation tool, the description adequately covers purpose, behavior, and expected return values. The sibling context and no output schema make this complete enough for an agent to select and invoke the tool correctly.

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 has zero parameters, so there is no parameter burden. Baseline for 0-param tools is 4, and the description appropriately focuses on behavior and return values rather than parameters.

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 uses a specific verb ('Create') and resource ('disposable email inbox') with a clear 24-hour expiration detail. It is clearly distinguishable from siblings like check_inbox, read_message, and download_attachment.

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 description implies the use case: creating a temporary inbox for receiving emails. It doesn't explicitly state when not to use it, but sibling names make the alternatives obvious, providing clear context.

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