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

With no annotations, the description carries the transparency burden. It does state a meaningful limitation ('without WHOIS or ownership data'), suggesting a pure syntactic operation. It does not mention how invalid hostnames are handled, whether any network access occurs, or that the many other schema fields appear to be discarded.

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. It immediately states the operation, the target resource, and an important scope boundary. Every word earns its place.

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?

The tool has a nine-parameter schema, no required parameters, no output schema, and no annotations. The description does not specify which parameter is the hostname input, what the return value looks like, or whether the other parameters are ignored. This leaves too much ambiguity for an agent to invoke the tool 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 description coverage is 100%, so the baseline is 3. The description maps naturally to the 'host' parameter, but it does not explain why eight other optional parameters exist or whether they should be ignored. The parameter descriptions themselves carry most of 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 specific verb ('split') and resource ('a hostname'), and clearly scopes the output to labels while excluding WHOIS or ownership data. This differentiates the tool from sibling shape-check tools such as github-repo-shape or figma-url-shape.

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 description implies when to use the tool: when you need hostname labels and explicitly do not need ownership data. However, it does not name alternatives or provide explicit criteria like 'use when...' or 'for ownership, use...', so the guidance is mostly implicit.

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