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

With no annotations, the description carries the burden of disclosing behavior. It states that the operation is a pure split and that ownership/WHOIS data is not involved, which implies a read-only, local transformation. However, it does not mention error behavior, output format, or whether the other schema parameters are ignored.

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 one short sentence with no filler: verb, resource, result, and a scope qualifier. It is front-loaded and every word contributes.

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, no required parameters, and a 9-parameter schema, yet the description provides no output or return information, no error semantics, and no clarification of which parameters are relevant. An agent would need to infer the expected input and result from the name and one schema field.

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 100%, so the baseline is 3; each parameter has a description. The tool description adds no parameter-level meaning beyond naming hostname, and it does not explicitly map hostname to the host parameter, though the schema's 'Public hostname' description makes the connection recoverable.

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 uses a specific verb (split) and resource (hostname) and names the output (labels), immediately distinguishing this from sibling shape and check tools. The qualifier 'without WHOIS or ownership data' also sets expectations about scope. This is a clear, standalone statement of purpose.

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 guidance is given about when to choose domain-shape over alternatives such as normalize-url, github-repo-shape, or url-ok tools. The only contextual clue is the negative scope 'without WHOIS or ownership data,' which does not tell an agent when to use this tool or what to use instead.

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