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

With no annotations, the description must disclose behavior. It states the tool splits hostnames and does not perform WHOIS or ownership lookup, which is a key behavioral limitation. However, it does not describe the output format or how the other eight parameters are handled, leaving significant behavioral ambiguity for those inputs.

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 that immediately states the core action. It contains no filler and is efficient for a simple purpose, though it may be too brief for the tool's actual complexity.

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 9 parameters, no output schema, and no annotations, so the description must carry substantial context. It only describes a hostname-splitting operation, but the schema includes many unrelated parameters (city, feed, json, path, query, etc.), suggesting the tool may have broader functionality that is entirely undocumented. The description is severely incomplete for an agent to know what the tool actually does with those parameters or what it returns.

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 schema descriptions (100% coverage), so the schema already documents each parameter. The description adds meaning only for the 'host' parameter (splitting into labels) but provides no additional context for the other eight parameters, which seem unrelated to the described purpose.

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 action ('Split a hostname into labels') and explicitly clarifies it does not include WHOIS or ownership data, distinguishing it from potential sibling tools that fetch such data. It clearly identifies the resource (hostname) and the operation (splitting).

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 a scope limitation ('without WHOIS or ownership data') but does not explicitly state when to use this tool versus alternatives. It does not name sibling tools or provide explicit 'use when' conditions, leaving the agent to infer the appropriate context.

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