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

With no annotations, the description carries the burden. It discloses one useful trait: no WHOIS or ownership lookup. It does not describe the return shape, invalid-hostname behavior, or whether it is read-only, but the word 'split' suggests a pure operation.

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 front-loaded sentence with no filler. Every word earns its place, and the qualifier 'without WHOIS or ownership data' is meaningful.

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 nine optional parameters and no output schema or annotations, yet the description only covers hostname splitting. It leaves agents uncertain about which parameter to use and what the result for the other parameters would be.

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. The description adds no parameter guidance and does not clarify why the schema exposes eight other optional fields (ref, url, city, etc.) when the tool is described as a hostname splitter.

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 names a specific verb ('split') and resource ('a hostname'), and defines the output ('labels'). It also distinguishes itself from ownership/WHOIS lookups and from sibling URL/shape tools.

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 intended use is implied: call when you need hostname labels without ownership data. However, it never explicitly states when to use this over alternatives such as normalize-url or web-fetch, nor does it name any exclusion conditions.

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