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

No annotations are present, so the description should carry the behavioral burden. It only indicates that WHOIS/ownership data will not be included. It does not say whether the call is read-only, how invalid hostnames are treated, whether labels are lowercased, sorted, or further normalized, or what happens if the input is not a hostname.

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 single sentence is frantically built to be short and front-loaded, with no wasted wording. However, for a tool with 9 parameters and no output schema, the description is still perhaps too terse to fully take advantage of the structured context.

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?

There is no output schema, no annotations, and nothing about the return format and validation behavior. For a tool with nine optional parameters and several very similar sibling tools, the description only describes a small subset of what the agent needs to know in order to call it correctly and confidently.

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 coverage is 100%, and the schema already describes each parameter, including note about discarding and no disk access. The description does not add beyond that, and it does not tell the agent which of the 9 properties is primarily relevant for the hostname label splitting operation.

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 core action: split a hostname into labels, and adds that it does not do WHOIS or ownership lookups. That is a specific verb-plus-resource statement, but it does not explicitly differentiate from the many sibling shape tools such as normalize-url, download-url-shape, or other shape tools.

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?

There is no when-to-use or when-not-to-use guidance. An agent has to infer that this is for hostname label splitting, which is insufficient given the large set of sibling tools like file-path-format, github-repo-shape, browser-url-ok, and normalize-url that could overlap from the standpoint of input and purpose.

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