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

Annotations already declare destructiveHint=true, readOnlyHint=false and idempotentHint=false, so the agent knows this is an irreversible-style mutation. The description adds one genuinely useful behavioral detail — that deletion does not block the sender — but says nothing about permissions required, permanence, or side effects on the conversation/history.

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?

One short, front-loaded sentence with the action first and the distinguishing constraint last. There is no filler and nothing that could be trimmed without losing 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 one-parameter tool with rich annotations and no output schema, the description is adequate but thin on the aspects that matter for a destructive operation: whether the deletion is permanent, whether the email can be recovered, and what the agent should expect afterward.

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% and the single emailId parameter is fully documented in the schema ('The id from list_external_mail'), which even cross-references the sibling listing tool. The description adds no additional parameter meaning, 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 (delete) and a specific, scoped resource (one email from the External tab). The phrase 'without blocking its sender' implicitly contrasts it with sibling operations like mark_external_mail_spam or list_blocked_senders, though no sibling is named explicitly.

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?

Usage is only implied: 'one email' and 'from the External tab' suggest single-item deletion from a specific mailbox view, and 'without blocking its sender' hints at when not to use spam/block flows. There is no explicit statement of when to prefer this over mark_external_mail_spam, move_external_mail_to_inbox, or list_external_mail.

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