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

Annotations already declare idempotency, non-destructiveness and open-world scope, so the description only needs to add context — which it does: it discloses the account-scope requirement, the permanence of the resource, the auth mechanism (Bearer header or key argument), and the recommended post-call verification step. It does not clarify reversibility (whether mail_disable truly undoes this) or what a successful enable returns, but it goes meaningfully beyond the structured hints.

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?

The purpose is correctly front-loaded, but the final two sentences about key retention and not sharing chats are near-verbatim duplication of the schema's key description, so the text carries redundant weight. The operational sequence (enable → status → credential) is well ordered and easy to scan.

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 two-parameter mutation with full schema coverage, no output schema and a rich annotation set, the description supplies the state-changing intent, prerequisites (account scope), auth options, and next-step navigation, which is enough to invoke it correctly. The only real gap is the absence of guidance about pre-existing mailboxes or how to interpret a failed/lost result beyond the schema's retry note.

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 both parameters are documented in detail, so the baseline is 3. The description's mention of 'a stable request_id' and the auth options largely restates what the schema already says about the request_id persist/retry contract and the key argument, adding little new meaning.

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 first sentence is a specific verb+resource statement ('Enable your permanent personal mailbox') that an agent can act on without opening the schema, and the word 'permanent' distinguishes it from a transient session action. Follow-up sentences implicitly differentiate it from siblings mail_status (a check, not a mutation) and mail_credential_create (IMAP/SMTP credentials are a separate step).

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 gives clear operational sequencing: call this, then 'Check mail_status afterwards', and use 'a separate mail credential for IMAP/SMTP' rather than expecting this tool to yield mail client credentials. What's missing is any exclusion — it never says what to do if a mailbox already exists, or whether mail_disable must precede a re-enable.

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