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

readOnlyHint=true is consistent and the description adds real context beyond the annotation: verified domains receive active testing (injection, XSS, SSRF, access control) while others get only passive checks. That behavioral distinction is not present in any structured field. It omits return shape/pagination, but for a zero-arg listing tool this is minor.

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?

Three short sentences, front-loaded with the core definition and followed by scope consequence and a next-step link. Every sentence carries information, though the opening fragment is slightly terse and the URL sentence is mildly promotional.

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 zero-parameter, read-only listing tool with no output schema, the description supplies enough: what the list contains and why it matters for scanning behavior. Only the return format (domain objects, pagination) is unspecified, which is a small gap.

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 clarify; per the baseline, this scores 4. The schema's empty properties object is consistent with the description's lack of parameter talk.

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 the resource precisely ('domains the user has proved they own') and conveys that this is a listing of them. It is clear what the tool returns, but it never explicitly names or contrasts a sibling (e.g. check_domain_verification or list_monitors), so sibling differentiation is left to inference.

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 implies usage by explaining that only verified domains get active testing, which tells the agent when the list matters, and it points to a URL for verifying more. However, it does not say when to call this versus check_domain_verification or start_domain_verification, so the routing guidance is only implied.

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