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

Beyond the annotations, the description discloses substantial behavior: the link is opened and paid by the account holder, a saved card is not charged, the mailbox and DNS records are set up after payment, and mail can be read/sent via webmail or IMAP/SMTP with credentials shown in the dashboard. This adds meaningful operational context that annotations alone do not provide.

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 description is front-loaded with the core action and key auth prerequisite, and every sentence contributes useful context for a tool that lacks an output schema. It is a single dense paragraph, but the length is justified by the complexity of the email setup flow.

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 tool with no output schema, the description is nearly complete: it covers the return value (a payment link), prerequisites, billing behavior, and post-payment setup. It does not address link validity, reusability, or failure cases, which are minor gaps rather than critical omissions.

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?

The schema already documents both parameters with examples and a default, achieving 100% description coverage. The description reinforces the meaning of the 'address' field (main inbox like hello@yourdomain.com) but does not add syntax or format details beyond what the schema provides.

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 description states a specific verb and resource: it returns a payment link that turns on email for a site's own domain. It is clear what the tool does, but it never explicitly contrasts itself with the sibling get_checkout_link, so an agent must infer the distinction from the word 'email'.

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?

The description gives prerequisites ('needs account token', 'site needs an active domain registered here first') and describes the payment flow, which implies when to use it. However, it does not explicitly say when to use this tool versus alternatives like get_checkout_link, email_status, or turn_off_email.

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