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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering safety and world-state assumptions. The description adds return semantics ('returns true if rentable') but little beyond that—no mention of how authoritative the check is or what factors could make availability change.

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 compact and front-loaded: purpose first, return behavior second, helpful tip last. The examples and phrase guidance are not redundant and earn their place.

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, read-only availability check with a rich input schema and output schema present, the description supplies enough context. No critical calling information appears missing.

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 coverage is 100% and the schema already explains domainId and subdomain clearly. The description's tip adds product-specific flavor about choosing a single lowercase label, but it does not materially clarify parameter meaning beyond what the schema already provides.

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 clear verb+resource: checking whether a specific subdomain is available on a domain, and explicitly says it returns true if rentable. It is distinct from search_domains and rent_domain at a glance, but it does not explicitly contrast itself with try_domain, leaving some potential overlap.

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 usage context is implied: check availability before renting a subdomain. However, there is no explicit guidance on when to use this tool versus try_domain or when not to use it. The tip focuses on choosing a good subdomain rather than tool selection.

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