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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is covered structurally. The description adds the non-obvious behavioral fact that the deletion is irreversible ('Cannot be undone'), which is genuinely useful context beyond the annotations, though it says nothing about permissions or side effects on the mailbox.

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 short sentences with zero waste; the destructive consequence is front-loaded as the first word of the description.

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 one-parameter, no-output-schema tool whose annotations carry the destructive/read-only profile, the description covers what it does and that it is irreversible. It omits how the target mailbox relates to the operation and any confirmation semantics, but nothing critical is missing.

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 coverage is 100% and the single 'mailbox' parameter is documented as 'Full mailbox address' in the schema. The description adds no meaning about which mailbox is targeted or how the Trash folder is resolved, so 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?

The description states a specific verb and resource ('Permanently delete every message in the Trash folder') and makes the scope (entire Trash folder, not individual messages) unambiguous. It does not name or differentiate itself from siblings like delete_message or restore_message, so it falls short of a 5.

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 conveys the bulk scope implicitly, but gives no guidance on when to use this versus delete_message for single messages, nor any prerequisite or confirmation requirement. The agent must infer the selection criteria.

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