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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds the detail about SSL/verification status, but does not disclose any additional behavioral aspects such as pagination, response format, or whether it returns system domains. This adds some value but is not rich.

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?

The description is one clear, front-loaded sentence that immediately conveys the primary action and scope. It contains no filler or redundancy, making it highly concise.

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 read-only list tool with no parameters and strong annotations, the description is largely complete. It specifies the resource (custom domains) and the included status fields. However, it does not describe the exact return shape or any pagination behavior, which would be helpful given no output schema is provided.

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?

The input schema has zero parameters, so schema description coverage is effectively 100%. Per the rubric, a baseline of 4 is appropriate for a tool with no parameters, and the description does not need to compensate for missing parameter information.

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 clearly states the tool lists all custom domains and includes their SSL/verification status. It uses the specific verb 'List' and identifies the resource ('custom domains'), which distinguishes it from sibling tools like scalix_domain_add and scalix_domain_verify that perform different operations.

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?

The description implies usage for listing domains but provides no explicit guidance on when to use it versus alternatives. It does not mention that scalix_domain_add is for adding domains or scalix_domain_verify for verification, so the context is inferred from the tool name and sibling list rather than stated.

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