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

With no annotations provided, the description bears full responsibility for behavioral disclosure. It only states the core action and a non-goal (no WHOIS/ownership), but omits any details about return format, error handling, side effects, or how the nine parameters are used. This is a significant gap for a tool with this many parameters.

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, clear sentence with no wasted words. It is appropriately concise for a simple operation, though it could be expanded with more context without becoming verbose.

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?

For a tool with 9 parameters, no annotations, and no output schema, the description is severely under-specified. It does not indicate which parameter is primary, what the output looks like, or how it relates to sibling shape tools. An agent would struggle to know exactly what to pass and what 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?

Schema description coverage is 100%, so every parameter already has a documented purpose in the schema. The tool description adds nothing about parameters, but the baseline of 3 applies because the schema does the heavy lifting. The description does not enrich parameter understanding.

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 a specific verb ('Split') and resource ('hostname into labels'), and adds a clarifying exclusion ('without WHOIS or ownership data') that hints at a boundary. However, it does not explicitly differentiate from sibling shape-checking tools like figma-url-shape or github-repo-shape, so it misses the top score.

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 on when to use this tool versus alternatives. It does not mention any conditions, prerequisites, or scenarios where it is preferred over other shape tools or URL/domain utilities. The agent is left to infer usage from the tool name alone.

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