add_sending_domain

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

With no annotations provided, the description carries the full behavioral burden. It discloses that two subdomains are provisioned, that the system chooses the right one per message, that this isolates marketing complaints from transactional delivery, and that risk_class changes the provisioning behavior.

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 action and output, then gives a compact explanation of the subdomain behavior and the risk_class condition. Every sentence adds necessary value with no filler.

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 only two parameters and no output schema, the description is complete: it explains what domain to provide, what happens by default, how risk_class changes behavior, and what the caller receives (DNS records to publish).

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?

Although the schema already covers both parameters at 100%, the description adds meaningful context: domain is the base domain under which mail.<domain> and news.<domain> are provisioned, and risk_class is used only to provision one subdomain on its own.

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 ('Register') and resource ('sending domain'), and clearly defines the expected output: DNS records to publish. It is easily distinguishable from sibling tools like list_sending_domains and verify_sending_domain.

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 clear context for supplying the sending domain and explicitly explains the condition for using risk_class: 'Pass risk_class only to provision one of the two on its own.' However, it does not explicitly name sibling alternatives or state when not to use this tool, so it stops 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.