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

With no annotations, the description must carry the behavioral burden. It does disclose one important non-behavior—no WHOIS or ownership lookup—and the core transformation is clear. But it does not describe the return shape, how the eight non-host parameters are handled, or any edge cases, so transparency is partial.

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 sentence with no filler and puts the core action first, followed by a clarifying exclusion. It is concise, though arguably too short for a tool with nine parameters and no output schema.

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, no annotations, and no output schema, yet the description covers only the hostname-splitting scenario. An agent is left without guidance on which parameter to pass, whether multiple parameters are allowed, or what result to expect, so the definition is substantially incomplete.

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; every parameter is already described in the input schema. The tool description adds no parameter meaning beyond 'hostname', and it does not clarify how the other parameters relate to the stated domain-splitting purpose.

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 states a specific action and object: 'Split a hostname into labels', and it usefully excludes WHOIS/ownership lookups, which helps distinguish it from ownership-oriented domain tools. However, the input schema exposes nine unrelated optional parameters, so the description does not explain the full scope of what the tool accepts, preventing a perfect 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 about when to choose this tool over sibling shape/validation tools such as github-repo-shape or jira-key-shape. The phrase 'without WHOIS or ownership data' hints at a use case, but it never states conditions, exclusions, or alternatives.

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