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 real value by disclosing exactly what the response contains (per-domain ownership state, TXT record, last-checked timestamp, last objection, platform hostname), which matters because there is 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?

Two sentences, information-dense but front-loaded with the return contents and closing with the actionable relationship to attach_domain. No filler, though the first sentence is a long pile-up of clauses.

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 carries the return-value burden and does so thoroughly. For a single-parameter read tool the only remaining gap is pagination/ordering behavior, which is minor.

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 coverage is 0% and project_id is undocumented in the schema, but the phrase 'the project's custom domains' conveys that the parameter scopes the list to one project. It adds modest meaning but never names or explains project_id directly, so it only partly compensates for the 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 the resource (the project's custom domains) and enumerates what is returned for each (ownership-check state, TXT record, last checked time, failure reason, platform hostname). It is specific and operational, though it never frames the verb 'list' and does not explicitly differentiate from check_domain, only from attach_domain.

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 a clear usage context: attach_domain returns the record only once, and this tool is how you verify whether attachment took. That tells the agent when to reach for it, but there is no explicit when-not or named alternative such as check_domain.

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