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

Adds valuable context beyond the annotations: deletes multiple messages, returns no body, reaches other callers' inboxes, and can destroy another caller's conversation. However, the blanket 'Permanently deletes' and 'cannot be undone' conflicts with the schema's `permanent` parameter, which allows moving to trash when false; that non-permanent path is not disclosed.

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?

Front-loaded with the core action and outcome, with safety warnings and alternative routing later. The description is a little long but every part earns its place; minor redundancy exists between 'Permanently deletes' and 'cannot be undone.'

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 dangerous cross-account behavior, return body, and scoped alternative very well. The missing piece is the `permanent: false` path and when a caller would want trash instead of permanent deletion, which is critical for safely invoking this tool.

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% (baseline 3), but the description misrepresents the `permanent` parameter by implying deletion is always permanent and irreversible. It does provide useful context that `thread_id` is the only identifier, but the misleading permanent/trash distinction drops it below baseline.

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 action ('permanently deletes a thread addressed by id alone') and resource ('every message in it'), and distinguishes it from the scoped sibling `delete_agentmail_inbox_thread` by explicitly naming that twin. An agent can tell what this tool does and how it differs.

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?

Provides explicit guidance: read first with `get_agentmail_thread`, warns that it affects inboxes created by other callers, and names the safer scoped alternative `delete_agentmail_inbox_thread`. This is clear when-to-use and when-not-to-use insight.

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