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

With no annotations present, the description carries full responsibility for behavioral disclosure. It reveals that the tool only produces labels and excludes ownership data, but it doesn't mention side effects, network usage, or output format. This provides some but not rich behavioral context.

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?

One sentence, zero redundancy, and the core action is front-loaded. Every word contributes to defining the purpose and a key constraint, making it highly efficient.

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 adequate for a simple tool but incomplete given the large schema. It does not specify which parameter to use (e.g., 'host') or describe the return structure beyond 'labels' – especially problematic since there is no output schema. An agent might struggle to assemble the correct call among the many unrelated parameters.

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 parameters at 100% coverage, so the baseline is 3. The description adds no additional parameter meaning beyond aligning loosely with the 'host' parameter; it does not clarify how the many other schema fields relate to the tool's operation.

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 uses a specific verb ('Split') with a clear resource ('a hostname') and a distinct non-goal ('without WHOIS or ownership data'). This precisely distinguishes it from sibling 'shape' tools like github-repo-shape or figma-url-shape, making the tool's purpose immediately identifiable.

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 (whenever a hostname needs splitting) and hints at an exclusion (no WHOIS/ownership), but it does not explicitly mention alternative tools or conditions for choosing between them. Usage context is inferable, not stated.

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