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

Beyond the annotations, which already indicate a non-read-only, non-idempotent, non-destructive operation, the description reveals the important post-registration requirement: DNS records (TXT token + MX) must be added before verification succeeds. This explains the pending state and prerequisite 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?

Two concise sentences front-load the core action and immediately give the next step an agent must know. There is no filler or redundancy.

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 one-parameter registration tool with annotations and an output schema, the description covers the essential workflow: register the domain, then add DNS records. Nothing critical is missing for correct invocation.

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 the single parameter 'name' with an example, providing 100% coverage. The description does not add extra parameter-level detail, but none is needed for such a simple parameter.

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 and resource: 'Register a new custom domain.' It clearly differentiates from sibling tools like domains.verify, domains.list, and domains.delete by describing the registration action rather than verification, listing, or deletion.

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 conveys when to use it by noting that DNS records must be added after registration before verification can succeed. This implies registration is a prerequisite for verification, though it does not explicitly name alternatives or state when not to use this tool.

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