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

With no annotations provided, the description carries the full burden. It discloses detailed behavioral semantics: return fields include id, name, added timestamp, ownership proof via email or DNS TXT with timestamps or absence, active status, and plan limit. This is substantial disclosure beyond the empty 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?

The description is front-loaded with the primary purpose and every sentence adds value. The field enumeration is detailed but directly relevant to using the tool correctly. No filler or redundant content.

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 zero-parameter listing tool with an output schema present, the description is complete. It explains what is returned, clarifies the meaning of ownership proof timestamps, and includes the plan-level limit. An agent can confidently invoke and interpret the result without further context.

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 tool has zero parameters and the schema confirms this. The description explicitly states 'Takes no arguments,' which satisfies the baseline for a no-parameter tool. No further parameter explanation is needed.

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 opens with a specific verb and resource: 'List every domain registered on your account.' It clearly differentiates from sibling tools like get_domain (single domain) and list_audits (audits, not domains).

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 clearly states this is for listing all domains on the account and that it takes no arguments. It does not explicitly name sibling alternatives or exclusion conditions, but the context is clear enough for an agent to select it when a full domain list is needed.

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