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

There are no annotations, so the description carries the full burden of behavioral disclosure. It only states that the tool operates 'without WHOIS or ownership data,' which is a negative constraint. It does not disclose whether the tool performs network access, what output format to expect, whether it is read-only, or how it handles the various parameter types. This is insufficient for a tool with no annotations.

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 short sentence, which is concise in length but under-specified for the tool's complexity (9 parameters, no annotations, no output schema). It lacks useful structure or front-loading of key information. Conciseness should not come at the expense of clarity; here it is too terse to be helpful.

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?

Given the high parameter count (9), zero annotations, no output schema, and no usage guidance, the description is severely incomplete. It does not explain what 'shape' means, how the tool processes different input types, what the output looks like, or any prerequisites or side effects. An agent cannot reliably call this tool correctly with the current information.

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%, and each parameter already has a clear description (e.g., 'discarded after the shape check'). The tool description adds nothing beyond a single mention of 'hostname' and does not clarify how the parameters relate to each other or which one is primary. Since the schema already documents each parameter, the baseline of 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 states a specific action (split a hostname into labels) and a resource (hostname), but it does not explain how this relates to the other eight diverse parameters (ref, url, city, feed, json, path, zone, query). It is not a tautology, but it leaves the tool's actual scope ambiguous and does not distinguish it from sibling shape tools like 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?

No guidance is provided on when to use this tool versus its siblings. It does not mention any alternative tools, conditions, or scenarios. The description is limited to a single action with no context on selection criteria, so an agent gains no help in choosing this over other 'shape' tools.

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