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 reveals that the tool does not provide WHOIS or ownership data; it says nothing about return format, invalid-hostname handling, network access, normalization behavior, or side effects. This is too thin for a tool with no annotation safety net.

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, front-loaded sentence with an active verb and no filler. The WHOIS caveat earns its place by clarifying scope. It is easy to scan and appropriately sized for its core message.

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 nine optional parameters, no output schema, and no annotations, the description is not complete enough for reliable invocation. An agent cannot determine what the expected output looks like, which parameter is the true input for hostname splitting, or how non-host parameters should be treated. The scattered 'discarded' notes in the schema help somewhat but are not connected to the description.

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; each parameter already has a meaningful description. The tool description adds the 'hostname' framing that maps to the 'host' property, but it does not explain why the other eight parameters exist or whether they are ignored. It neither substantially compensates for nor worsens the schema information.

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 verb and resource: 'Split a hostname into labels'. It also draws a boundary by adding 'without WHOIS or ownership data', which helps separate it from domain-lookup tools. However, it does not reconcile this clear purpose with the schema's nine unrelated optional parameters, which creates some ambiguity.

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 use case is implied: use this tool when you have a hostname and need it split into labels. The 'without WHOIS or ownership data' caveat acts as a scope exclusion, but no alternative tool is named and there is no guidance about which of the nine optional parameters to provide. It is enough to infer basic usage, but not enough to disambiguate the broad schema.

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