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. The description adds genuinely useful behavior beyond that: the default is a recoverable move to Trash, and only Trash/Drafts items or an explicit permanent:true flag cause irreversible deletion.

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, front-loaded with the action and then the default-vs-permanent distinction. No filler; every clause carries decision-relevant information.

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 destructive tool with no output schema, the description covers the key recoverability question (Trash vs permanent) and the trigger condition. It omits permission/auth requirements and any note that restore_message can recover the soft-deleted case, so it is slightly short of fully complete.

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%, so the baseline is 3, but the description adds meaning by explaining how the permanent flag interacts with folder context (Trash/Drafts), which the schema's one-line 'Permanently delete instead of moving to Trash' does not convey.

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+resource ('Delete a message') and immediately clarifies the two deletion modes, which distinguishes it from siblings like move_message, empty_trash, and restore_message. It does not name those siblings explicitly, so it stops 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?

Gives an implicit condition for permanent deletion ('from Trash/Drafts or with permanent: true'), which helps an agent choose the right mode, but offers no guidance on when to use this tool versus move_message, empty_trash, or restore_message.

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