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

With no annotations, the description carries the burden of behavioral disclosure. It does state that the tool configures the domain and imposes an auth requirement, but it omits effects such as whether domain email settings are overwritten, whether a confirmation step follows, or whether the operation is reversible.

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 short, action-first, and the access block is relevant rather than filler. It could be slightly cleaner, but every sentence earns its place.

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 configuration tool with no annotations and no output schema, the description covers the key prerequisites and auth path. It is still incomplete around post-call behavior and how this step fits with sibling verification/confirmation tools.

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%, so the baseline is 3. The description's 'custom address' phrase reinforces from_email, but it adds no format or relationship detail beyond the schema's Domain ID and Custom from email address descriptions.

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 uses a specific verb ('set up') and resource ('email sending for a verified domain'), and clarifies the action further by saying it configures the domain for sending verification emails from a custom address. It does not explicitly name sibling tools, but the action is distinguishable from check/start/confirm domain email operations.

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 states clear prerequisites: the domain must be verified and a Proof account is needed, and it describes the authentication flow required before calling. It does not explain when to choose this over nearby siblings such as check_domain_email_status, start_domain_email_verification, or confirm_domain_email_code, so the usage context is implied but not explicit.

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