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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It reveals one behavioral trait—no WHOIS or ownership lookup—but says nothing about side effects, network access, error behavior, or what happens with the many other accepted inputs. For a tool with 9 optional parameters, this is insufficient transparency.

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 front-loaded sentence with no filler, and the key qualifier 'without WHOIS or ownership data' is stated immediately. It is concise, though the brevity undersells the schema's complexity.

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?

This tool has 9 optional parameters, no required fields, no annotations, and no output schema, yet the description gives only a one-line hostname example. An agent is not told what to pass, what the return value looks like, or how to choose between domain-shape and the many sibling shape-checking tools.

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 already documents all 9 parameters with 100% coverage, including discard behavior and 'no disk access', so the baseline is met. The description adds only a hostname-related hint and does not clarify how the other parameters map to tool behavior, but the schema carries the semantic weight.

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 names a concrete operation—split a hostname into labels—and adds a useful qualifier about excluding WHOIS or ownership data. However, the input schema exposes 8 other parameters (url, city, feed, json, path, zone, query, ref) that the description never ties to the tool's purpose, so the true scope is ambiguous.

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 'without WHOIS or ownership data' implies a lightweight syntactic use case and hints at when not to use the tool, but no alternatives or explicit exclusions are mentioned. Sibling tools such as normalize-url, github-repo-shape, and validate-json are not referenced, so an agent must infer when this tool is appropriate.

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