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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the core split operation and a negative constraint, but it does not explain the output format, whether network access occurs, how the nine optional parameters are handled, or what happens when the hostname is invalid.

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, front-loaded sentence with no filler. Every word contributes either the operation or a meaningful limitation.

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?

Despite a 9-parameter schema and no output schema, the description does not specify which parameter to supply, what the returned labels look like, or any error/edge-case behavior. An agent would have difficulty confidently invoking this tool correctly without additional context.

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 each parameter is already documented. The description adds a useful hint that 'hostname' maps to the host parameter, but it does not clarify the role of the other eight accepted parameters or how they relate to this tool. Baseline 3 is appropriate.

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 and resource: split a hostname into labels. The qualifier 'without WHOIS or ownership data' helps distinguish it from ownership/enrichment tools, though it does not explicitly contrast it with sibling URL- or hostname-related 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 guidance about when to use this tool instead of normalize-url, browser-url-ok, playwright-url-ok, or similar siblings. The 'without WHOIS or ownership data' phrase implies a non-enrichment use case, but no explicit when/when-not or alternative is given.

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