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

The annotations already declare destructiveHint=true and idempotentHint=true, but the description adds real value beyond them: it discloses what is destroyed (message files and attachments), the authorization level required, and a reassuring boundary ('Separately copied files are unaffected'). It stops short of saying whether the deletion is recoverable or goes to a trash state, which matters given the mailbox_archive sibling.

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, each carrying distinct information: action+scope, prerequisite, safety confirmation, and boundary condition. The destructive scope is front-loaded with no filler.

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?

Covers the action, its cascading effects, required permissions, and a user-confirmation safety step, which is what an agent needs before invoking a destructive, non-reversible-in-appearance operation. An output schema exists, so return values need not be described.

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, email_id, account_id, and reason, including the cross-account authorization caveat. The description adds nothing about parameter formats or constraints, so the baseline 3 applies.

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 and resource ('Delete one email') plus the cascade scope ('its owned message files and attachments'), which distinguishes it from whole-mailbox operations. It never names a sibling tool explicitly, so the differentiation from mailbox_delete_permanently or mailbox_archive is left to inference.

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?

Gives a clear prerequisite ('Requires mailbox-admin access') and an operational condition ('Confirm the target with the user before calling'). It does not name alternatives such as mailbox_archive for reversible removal or mailbox_delete_permanently for mailbox-level deletion, so the when-not case is missing.

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