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

With no annotations, the description carries the burden of explaining behavior. 'Check' and 'returns true if free to claim' convey read-only, boolean semantics, but the description does not explicitly state false/error behavior, whether the check reserves the name, or that availability may change before a later create call. Adequate but not rich.

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 with no filler. It states the operation, the resource, the context, and the return condition in an efficient way.

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 simple two-parameter check tool with no output schema, the description provides the key return condition and clarifies the relationship between subdomain and domain. It falls just short of a 5 because it does not explicitly define the false/error return value or warn that availability is not a reservation.

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 covers both parameters with descriptions and examples, so schema description coverage is 100%. The tool description adds little beyond confirming that the subdomain is checked 'under a given domain,' so the baseline score of 3 is appropriate.

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 ('Check if') and identifies the exact resource ('subdomain name ... available for registration under a given domain'). It also states the return value, making it clearly distinct from sibling tools like create_subdomain, delete_subdomain, or list_subdomains.

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 phrase 'available for registration' implies this is a pre-flight check before create_subdomain, and the tool is clearly the only one of the siblings that checks availability. However, it never explicitly says 'use before create_subdomain' or mentions when not to use it, leaving the agent to infer the intended workflow.

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