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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only states that WHOIS and ownership data are not included, which is a negative constraint, but it does not disclose side effects, return format, or what happens with the various input parameters. For a tool with no annotations and a broad schema, this is a significant gap.

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 sentence, which is efficient in terms of word count and is front-loaded with the primary action. However, it is so short that it under-specifies the tool's behavior. It is concise but not appropriately sized for the complexity of the tool, so a 3 is appropriate.

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 9 optional parameters, no output schema, and no annotations, making it relatively complex. The description covers only one narrow behavior (hostname splitting) and does not explain how the other parameters are handled, what the tool returns, or what side effects (if any) occur. This is inadequate for an agent to use the tool correctly across its parameter space.

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 all 9 parameters have individual descriptions in the schema. The tool description adds no additional meaning about the parameters; it only mentions hostname splitting, which relates to the 'host' parameter. Since the schema already documents each parameter, the baseline is 3, and the description provides no extra value.

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 verb 'Split' and the resource 'hostname', and adds a constraint 'without WHOIS or ownership data', which conveys a specific scope. However, it does not differentiate from sibling tools like normalize-url or browser-url-ok, and the input schema includes many unrelated parameters, suggesting the description may not cover the full tool scope. It is not a tautology, so it earns a 4.

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 description provides no guidance on when to use this tool versus alternatives. It does not mention conditions, prerequisites, or exclusions. With 28 sibling tools, an agent would have no reason to select this one based on the description alone.

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