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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so the safety profile and the fact that this reaches outside the system are covered. The description adds the useful detail that the response includes diagnostic categories plus remaining remediation steps, but says nothing about latency, caching, or whether stale DNS results can be returned — relevant for an external-lookup tool with no output schema.

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 compact sentence, front-loaded with the verb and resource, with the reported status categories listed efficiently. Nothing is wasted and nothing important is buried.

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 read-only diagnostic with no output schema, the description conveys both the scope of the check and the shape of the answer (statuses plus outstanding requirements). Only the return format specifics and any external-lookup caveats are missing, which is a minor 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?

There is a single parameter with 100% schema description coverage that already explains it accepts a site slug or id. The description adds no further meaning about the parameter, which is acceptable at full schema coverage but is a baseline rather than an enhancement.

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 names a specific verb ("Check") and resource ("custom domains") and enumerates exactly what is inspected: DNS, nameserver, and certificate status. That clearly separates it from add_custom_domain and remove_custom_domain, though it does not explicitly name those siblings as alternatives.

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 rather than stated: the mention of "what is still needed" suggests calling it after configuring a domain to verify readiness. There is no explicit when-to-use, no prerequisites, and no mention of how it relates to check_site, which also performs a verification-style check.

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