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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=true and openWorldHint=false, so the safety profile is covered. The description adds that this pushes a request to the external Resend service immediately ('now') and refreshes status, which is useful context beyond the annotations, but it doesn't cover whether verification is async, how long it takes, or what failure looks like.

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 sentence, front-loaded with the action and with no filler. It is efficient, though the trailing 'after its DNS records were added' clause slightly crowds the core statement.

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 single-parameter mutation with full schema coverage and annotations covering safety, no output schema needed, the description supplies the essential trigger context. It is complete enough to call correctly, with only the async/verification lifecycle 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 description coverage is 100% for the single domainId parameter, so the baseline is 3. The description adds nothing about the parameter's format or where to obtain the ID, so it earns no credit above baseline.

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 names a specific verb (verify) and resource (email domain) plus the actor (Resend), so the agent knows exactly what operation runs. It stops short of distinguishing itself from near siblings like check_mail_domain and update_mail_domain, which the agent would have to sort out on its own.

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 a clear trigger condition: run this 'after its DNS records were added.' That is genuine when-to-use guidance. It does not name alternatives or state when not to use it (e.g., vs. check_mail_domain), so it falls short of a 5.

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