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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds meaningful behavioral detail by disclosing the exact payload shape (statuses including pending/verifying/active/error, the DNS record, the default-domain flag, and limits.used/limits.max). It omits empty-state behavior and auth specifics, keeping it short of a 5.

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 dense sentence front-loads the resource and then enumerates return fields, with no filler or repetition. It is long for a single sentence, but every clause carries distinct information (statuses, DNS record, default, limits).

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?

There is no output schema, so the description must carry the return-value burden, and it does so thoroughly. The only remaining gaps are operational details such as empty-domain handling and whether results are ever paginated, which are minor for a zero-parameter list call.

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 tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description correctly avoids inventing parameters and instead spends its words on what the tool returns.

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 precisely identifies the resource (custom domains) and enumerates what is returned: statuses, DNS record, default flag, and plan limits. The verb is only implied by the tool name, and no sibling tools are named, but the scope is unmistakable against the link/account siblings.

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?

Usage is implied through the plan note ('Business and Enterprise plans'), which tells an agent who this applies to. However, there is no explicit when-to-use guidance, no statement of prerequisites beyond the plan, and no named alternative for situations where this tool is not appropriate.

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