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

With no annotations provided, the description carries the behavioral disclosure burden. It does disclose a meaningful boundary—no WHOIS or ownership lookup—but it does not describe return format, handling of invalid hostnames, or whether any normalization occurs.

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 no filler. Every word contributes to explaining the tool's purpose and its key limitation.

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 description is minimally viable for a simple hostname-splitting tool, and the schema documents the relevant 'host' parameter. However, with nine optional parameters and no output schema, it leaves some ambiguity about exactly which parameter should be supplied and what the returned labels look like.

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?

All 9 parameters have descriptions in the schema, including 'host' described as 'Public hostname', which aligns with the tool's purpose. The description itself adds no parameter-level detail, but the schema already covers parameter meaning, so a baseline score 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 clearly states a specific action ('split') on a specific resource ('hostname') and adds a useful non-goal ('without WHOIS or ownership data'). It is not fully explicit about how it differs from sibling URL/shape tools, but the core purpose is unambiguous.

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 implies when to use the tool: when only hostname label splitting is needed and WHOIS/ownership data is not required. However, it does not name alternative tools or provide explicit when-to-use vs. when-not-to-use guidance.

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