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

Adds substantial context beyond the annotations: the three things being verified, that nameservers are queried directly so new records count immediately, that CDN/reverse-proxy fronting is supported, and that `failureMessage` differentiates the three failure modes. It also discloses a real side effect — the first active custom domain is auto-promoted to primary — which explains the non-idempotent, non-read-only annotation profile rather than contradicting it.

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?

Front-loaded with the core action, then layered with failure semantics, polling guidance, and the promotion side effect. The re-check schedule detail is verbose but earns its place by informing polling decisions; only that sentence is borderline expendable.

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?

With no output schema, the description still tells the agent what comes back (updated status) and how to interpret `failureMessage`. The only meaningful gap is the absence of any explanation of the two required identifiers.

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?

Schema description coverage is 0% and the description never mentions `websiteId` or `domainId` — no hint about where to obtain them or whether the domain must already exist. The parameter names are largely self-explanatory, which prevents a 1, but the description does nothing to compensate for the total coverage gap.

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 (re-checks) plus the exact resources inspected: ownership TXT record, edge readiness, and HTTPS reachability of the hostname. This is clearly distinguishable from siblings like websiteDomains_createCustomDomain, websiteDomains_list, and websiteDomains_setPrimaryDomain.

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 strong context for when to call it (after DNS records are set, when polling for activation) and implicitly when not to over-poll by disclosing the automatic re-check schedule. It does not explicitly name a sibling alternative or state a hard 'do not use' condition, which keeps it just 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.