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

No annotations are provided, so the description carries the full burden. It discloses the exclusion of WHOIS/ownership data, but says nothing about the behavior for the other 8 parameters, the return format, or side effects. This is a minimal disclosure for a tool with such a broad parameter set.

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?

A single sentence with no filler. It front-loads the core action and the key exclusion, making it easy to parse.

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?

For a tool with 9 optional parameters, no annotations, and no output schema, this description is drastically incomplete. It does not explain why parameters like 'city' or 'feed' are relevant to splitting a hostname, nor what the tool returns. An agent cannot reliably invoke this tool correctly based on this description alone.

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?

The input schema already describes all 9 parameters with specific details (e.g., 'discarded after the shape check'). The tool description adds no additional parameter information, so it stays at the baseline for high schema coverage.

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 ('Split') and resource ('hostname') and clarifies it excludes WHOIS/ownership data, which distinguishes it from sibling shape tools. However, the input schema contains 9 unrelated parameters (city, feed, json, etc.) that contradict the narrow hostname focus, creating confusion about the tool's true scope.

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 gives a negative constraint ('without WHOIS or ownership data') but does not name any alternative tools or conditions for when to use this tool vs others. With 28 siblings, this is insufficient routing information.

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