Registration and availability

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds meaningful behavioral context: it queries each registry's RDAP server, handles up to 20 domains, and resolves subdomains to their registrable domain. No contradiction with annotations.

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 a single dense sentence, front-loaded with the core action and a colon-separated list of returned data. It is compact with no filler, though the subdomain behavior is tacked on at the end without a clear structural break.

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?

Given the simple read-only nature, an output schema exists (so return values are covered), and annotations handle safety, the description is largely complete. It still lacks guidance on error scenarios and sibling differentiation, but covers core behavior and input constraints well.

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 description coverage is 0%, so the description carries the burden for parameter meaning. It explains that the 'domains' array accepts domain names, that subdomains are normalized to registrable domains, and that up to 20 are allowed. This adds value beyond the raw schema constraints.

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 states the tool retrieves registration/availability data from RDAP, listing specific fields like registrar, dates, DNSSEC, and name servers. It is clear enough to distinguish from sibling tools (check_dkim, check_spf, dns_lookup), though 'Registration of' is slightly awkward phrasing and not an explicit verb like 'retrieves'.

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?

No explicit guidance is given about when to use this tool versus alternatives like dns_lookup or domain_report. The description implies a registration-info use case but does not state when to prefer it, what scenarios it should not be used for, or how it differs from sibling tools.

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