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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, covering safety. The description adds useful behavioral content above that bar by disclosing what the response contains (expiry dates and status) and confirming the result is limited to the caller's own holdings.

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 sentence with the resource, scope and return contents front-loaded, and no filler or redundancy.

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 no-param, read-only list tool with no output schema, the description does the important remaining work by stating which fields come back (expiry, status). The only gap is the absence of explicit routing against the search/purchase siblings.

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 takes zero parameters, so there is nothing for the description to disambiguate; baseline for a 0-param tool is 4.

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 a specific verb and resource ('List the domains owned by the caller') and names the returned fields ('expiry dates and status'). It doesn't explicitly differentiate from the sibling search_domains, so an agent must infer that this lists already-owned domains rather than searching available ones.

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 phrase 'owned by the caller' implies account-scoped usage with no arguments, which is adequate implied guidance. There is no explicit statement of when to prefer this over search_domains or whois_lookup, and no prerequisites or exclusions.

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