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

With no annotations, the description bears the burden of disclosing side effects and access patterns. It only says the tool operates 'without WHOIS or ownership data,' which hints at no ownership lookup, but it does not state whether it is read-only, makes network calls, or persists anything. The schema-level 'discarded' notes are not part of the tool description.

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, focused sentence with no wasted words. It could be improved by adding an example or clarifying the input field, but it is appropriately concise.

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?

There is no output schema, and the description does not explain the return format, error behavior, or which of the nine optional parameters is required/expected. This leaves important context missing for a tool with an ambiguous parameter list.

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. The tool description adds little parameter-specific meaning, and the schema contains many unrelated optional fields, but the 'host' parameter is at least described as 'Public hostname', so an agent can infer the intended input.

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 the action ('Split a hostname into labels') and resource ('hostname'), and the negative scope ('without WHOIS or ownership data') helps distinguish it from ownership lookups. However, it does not specify which input parameter carries the hostname, and the sibling context includes several shape tools, so it is not maximally disambiguating.

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 about when to use this tool instead of sibling tools such as normalize-url, browser-url-ok, or other *-shape tools. The description states what it does but not the circumstances or alternatives.

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