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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds real behavioral context beyond them: the tool reports the required DNS record, whether DNS resolves, and that TLS is issued automatically once it does. The one gap is the not-configured case — it doesn't say what comes back when no custom domain exists.

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?

A single front-loaded sentence where each clause contributes return-value information; the parenthetical about TLS earns its place as scope clarification. Slightly dense, but no filler.

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 burden of explaining the return payload and does so concretely (status, DNS record, resolution flag, TLS). Only the empty/not-set state and error behavior are left unspoken.

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 100% for the single 'id' property, and the description's phrasing 'a project's custom domain' reinforces that the identifier is a project UUID. Minimal added syntax, but no ambiguity remains.

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?

Names a specific verb and resource ('Get a project's custom domain') and immediately enumerates the returned facets (status, DNS record, resolution state), which distinguishes it from mutation siblings set_custom_domain and remove_custom_domain. It does not explicitly position itself against lookup_domain or check_subdomain, which look closely related.

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 only implied by the read verb; there is no explicit statement of when to call this versus lookup_domain, check_subdomain, or set_custom_domain. An agent can infer it is the read path, but nothing confirms the boundary.

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