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

Annotations flag destructiveHint=true, but the description is what explains the destruction concretely: 'Clears the same domain from any other account's unverified claim.' It also discloses the DNS lookup (open-world behavior) and the propagation-delay failure mode. It stops short of covering idempotency semantics or any rate limits.

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?

Four short clauses, action first, with the Premium gate and the failure-mode caveat following. Informal but no wasted sentences; the only weakness is the fragmentary 'Part of Premium.' clause, which reads more like a note than a structured precondition.

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?

An output schema exists, so return values need not be explained. The description covers the plan requirement, the cross-account side effect, and the expected transient failure, which is most of what an agent needs, with the parameter format being the notable omission.

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?

One parameter with 0% schema description coverage, so the description carries the full burden and it doesn't deliver: it never states whether 'domain' is an apex domain, a subdomain, or includes a scheme/path. 'Look the domain up in public DNS' only weakly implies the parameter is a hostname.

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 concrete verb and resource ('look the domain up in public DNS') plus the consequential effect ('switch the page to it', 'kulhad.co/<name> then redirects there'). It doesn't explicitly name distinguish it from the sibling get_custom_domain or set_custom_domain, so it falls just short of a 5.

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?

Gives useful preconditions and expectations ('Part of Premium', 'Fails until the record has propagated, which is normal for the first few minutes'), which implies it belongs in a post-DNS-setup flow. However, it never says when to prefer this over set_custom_domain or get_custom_domain, 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.