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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the safety profile is covered. The description adds the useful state transition (archived -> active list) and scoping to a single mailbox, but says nothing about permissions, error behavior if the mailbox is not archived, or repeat-call effects.

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 front-loaded sentence with zero filler, appropriately sized for a simple state-change tool.

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?

With an output schema present, annotations covering the safety profile, and full schema description coverage, the definition is nearly complete for a low-complexity mutation. It only lacks guidance on failure conditions (e.g., unarchiving a mailbox that is not archived) and the reason/account_id usage context that agents might want.

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 the schema already documents mailbox_id, account_id, and reason. The description only implies that exactly one mailbox is affected ('one archived mailbox'), which is a marginal addition over the required mailbox_id field.

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 a specific verb (restore/unarchive) and resource (one archived mailbox), and the state transition target (active mailbox list) is explicit. It reads as the clear inverse of the sibling mailbox_archive, though it never names that sibling or otherwise distinguishes itself from it.

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?

No guidance on when to use this versus alternatives, no prerequisites, and no mention of the corresponding mailbox_archive tool or the conditions under which an unarchive is appropriate. The usage context is only implied by the verb.

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