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

Annotations already declare the tool as read-only, idempotent, and non-destructive, lowering the bar. The description adds behavioral context by specifying it returns registration status and expiration date, with the latter conditional on registration. This goes beyond the annotations, though it doesn't mention rate limits or other operational details.

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 tool's purpose and key outcome. Every word contributes value, and the structure is 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?

For a simple tool with one parameter, a clear output schema, and thorough annotations, the description covers the essential use case. It explains what the tool does and what result to expect without unnecessary detail.

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 has 100% coverage, with the 'domain' parameter already described and exemplified. The description does not add additional parameter semantics beyond what the schema provides, so the baseline 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 clearly states the tool's function: checking if a domain is registered or available, and returning registration status and expiration date. The verb 'check' and resource 'domain' are specific, but it does not explicitly distinguish itself from sibling tools like domain_lookup or find_available_domains, which may have overlapping functionality.

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 lightweight, quick check, giving clear context for when to use it. However, it lacks explicit exclusions or alternatives, such as noting when to use domain_lookup or find_available_domains instead, which would be valuable given the large sibling list.

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