Check domain availability

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

Beyond the readOnlyHint annotation, the description discloses non-obvious routing behavior ('does NOT route by who holds the domain'), provider-specific limitations, and quota implications. This adds significant behavioral context that annotations alone do not convey, with no contradictions.

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 longer than average but every sentence contributes unique information: main purpose, routing semantics, provider capabilities, and quota impact. It is front-loaded with the core purpose and avoids redundancy, though slightly dense.

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?

Given the multi-provider complexity, the description covers purpose, routing logic, provider limitations, batch behavior, and account-threshold nuances. Since an output schema exists, return-value details are appropriately omitted, making the description complete for this tool.

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%, so the schema already documents both parameters well. The description adds contextual color about provider behavior (e.g., batch vs. single-request) but does not materially enhance the meaning of the domains or provider parameters beyond what the schema states.

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 opens with a specific verb and resource: 'Check whether one or more domains are available to register,' clearly distinguishing this from sibling tools like get_domain_pricing or list_domains. It also scopes the operation to availability, which is a distinct registry-level query.

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 provides explicit when-to-use and when-not-to-use guidance: it explains that availability is registry-level rather than account-level, states that Route 53 cannot answer, and contrasts Namecheap's batch capability with GoDaddy's per-request quota cost. This effectively routes the agent toward the correct provider choice.

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