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

Annotations already cover readOnly, idempotent, non-destructive, and non-open-world, so the description adds real value with '(needs account token)' for the auth requirement and 'Does not charge' to signal no billing impact. 'Read-only' merely restates readOnlyHint and 'No passwords' is a mild oddity, but overall it contributes context beyond the structured fields.

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 auth note and the primary action, then the returned fields. Slightly run-on and contains some redundancy ('Read-only' duplicating the annotation), but no sentence is wasted.

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?

With no output schema, the description carries the burden of explaining return values and does so well (addresses, mailbox vs forwarding, status, price, next step). Auth requirement is flagged, so an agent has enough to call it correctly, with only sibling routing left unstated.

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 the single 'site' parameter is fully documented there, so the description need not explain it. It adds nothing about parameter format beyond the schema, giving the baseline 3 for a well-covered single param.

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 (Returns) and resource (the email on a site's own domain) and enumerates the returned fields: address, mailbox vs forward, status, monthly price, and next step. It does not explicitly differentiate itself from siblings like site_status or the email-management tools, so it lands just below the top tier.

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 implies a read/status-check use case but never says when to call it versus alternatives such as turn_off_email, remove_email_address, or site_status. Usage is inferable but no explicit condition or exclusion is given.

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