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

Annotations only supply readOnlyHint=false, destructiveHint=false, openWorldHint=false; the description adds substantially more: refusal to guess the target account, idempotent no-op when the folder already exists, and verification against the account's folder list before reporting success. These are exactly the traits an agent needs before issuing a mutation.

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?

Four sentences, front-loaded with the core action and then the constraints; each sentence carries a distinct rule (account requirement, idempotency, verification, confirm gate). Slightly dense but nothing is redundant.

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 3-parameter mutation with an output schema already present, the description covers everything needed: target scope, conditional parameter requirement, idempotency behavior, verification of success, and the preview/commit gate. No significant gap remains.

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%, so the baseline is 3, but the description adds real meaning beyond the terse schema text: `account` becomes conditionally required rather than merely 'optional, uses default', and `confirm` false/omitted is documented as a preview mode rather than just 'must be true to create'.

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 with scope: creates a mailbox folder in the Mac's Apple Mail, in exactly one account. An agent can distinguish this from list_email_folders and from m365/Outlook folder tools without opening a schema.

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?

Explicitly states when `account` is required (multi-account setups) and names list_email_accounts as the way to discover names, plus a clear when-to-pass-confirm rule (omitted = preview, confirm=true = create). Alternatives and conditions are spelled out rather than inferred.

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