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

With no annotations, the description carries the behavioral burden. It discloses the core operation and a meaningful non-behavior (no WHOIS/ownership), but it does not state the output format, invalid-hostname handling, or the fact that most of the optional schema fields 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?

One clear, front-loaded sentence with no wasted words; the negative scope is useful and not padding.

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 nine optional parameters and no output schema, but the description does not identify which parameter is meaningful or what the labels look like when returned. An agent could pass the wrong parameter and not know what return shape to expect.

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 has 100% description coverage and all parameters are documented, so the baseline is 3. The description only reinforces that 'host' is the relevant input without adding parameter-level detail.

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'), a specific resource ('a hostname'), and an explicit negative scope ('without WHOIS or ownership data'), so the agent knows exactly what the tool does and what it deliberately avoids. This distinguishes it from other shape tools like github-repo-shape or normalize-url.

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 'without WHOIS or ownership data' clause implies this is for label splitting only when ownership metadata is not needed, but no alternative tool is named and no explicit when-to-use/when-not-to-use guidance is given.

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