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

With no annotations, the description must fully disclose behavior. It only mentions that the tool avoids WHOIS/ownership data, which is a partial disclosure. It does not explain what happens with the other 8 parameters (are they ignored? validated? cause errors?), nor does it describe return values or side effects. This is insufficient for an agent to safely invoke the tool.

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 concise, but it omits critical information about the tool's actual scope. It is under-specified rather than efficiently concise, since it fails to address the multi-parameter schema and the behavior for non-host inputs. It does not front-load the fact that other parameters exist.

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, the description is completely inadequate. An agent cannot determine which parameters are actually used, what the tool returns, or how it behaves with inputs like 'city' or 'json'. The description covers only a fraction of the tool's surface area and leaves most usage ambiguous.

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% – each of the 9 parameters has a description in the input schema, so the schema already documents them. The tool description adds no extra meaning beyond mentioning 'hostname', which maps to the 'host' parameter. Per the baseline, 3 is appropriate because the schema carries the semantic load, and the description does not enrich it.

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 and resource ('Split a hostname into labels') and notes it lacks WHOIS/ownership data, which is clear for that narrow function. However, the input schema accepts 9 unrelated parameters (ref, url, city, feed, json, path, zone, query), so the description is misleading about what the tool actually operates on. It does not distinguish from sibling tools like github-repo-shape or jira-key-shape, which likely perform similar shape checks.

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?

There is no guidance on when to use this tool versus alternatives. It does not mention any sibling tools, conditions, or exclusions. The description gives no context about which inputs are relevant or how to choose between this and other 'shape' tools.

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