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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered. The description adds value beyond that by disclosing the exact return shape (id, hostname, verified, misconfigured, updatedAt), which is meaningful for a read tool with no output schema; only pagination/ordering behavior is left unstated.

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?

Three short sentences, front-loaded with what the tool does, followed by the return shape and the motivating use case. No filler, no repetition of the title, and each clause carries information an agent can act on.

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 single-parameter read tool with no output schema, the essentials are covered: scope, return fields, and purpose. It is nearly complete, with only minor gaps around result ordering and whether the list is ever paginated or truncated for projects with many domains.

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 (projectId) and schema description coverage is 100%, so the schema already documents it completely. The description implies the domains are scoped to the supplied project but adds no format, default, or constraint detail beyond the schema, which is the correct baseline of 3.

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 gives a specific verb and resource ("Lists a project's custom domains") and even enumerates the returned fields, so an agent knows exactly what it gets. It does not need to distinguish itself from a competing domain sibling because none exists in the tool list, but it also makes no explicit routing statement, which is the only thing separating it from 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?

"Use to check whether a domain is verified or misconfigured" gives a concrete purpose-driven use case rather than leaving intent implied. It stops short of stating when-not-to-use it or naming an alternative (e.g., a hypothetical get_domain or verify_domain tool), so it lands at clear-context-without-exclusions.

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