domains_check_availability

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

No annotations are provided, so the description carries the full burden. It explicitly declares 'Read-only' which is valuable behavioral context for a check operation. However, it does not describe what the response contains, how SPEED differs from ACCURACY in terms of latency or thoroughness, or any edge-case behavior. The safety trait is covered, but broader behavioral expectations are absent.

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?

Two sentences with no filler. The purpose is front-loaded, followed by the one required parameter format and the single optional parameter's options. Every word contributes to correct invocation.

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 tool with no output schema, the description gives enough to call it correctly: domain format and the meaning of optimizeFor. It does not describe the return shape, but for an availability check the result is predictable enough that this is a minor gap. The absence of any note on invalid domains or timeout behavior keeps it from a 5.

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 baseline is 3. The description adds value beyond the schema by explaining the 'optimizeFor' enum in plain language: SPEED is 'a fast check' and ACCURACY is 'a careful one'. It also reinforces the domain format with an example. This practical nuance exceeds the schema's terse enum labels.

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 begins with a specific verb-resource pair: 'Check whether a domain name is available to register.' This clearly identifies the tool's function and distinguishes it from siblings like domains_suggest (which suggests domains), domains_get_quote (pricing), and domains_prepare_registration (registration workflow). No ambiguity remains.

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 gives clear operational context: pass a fully qualified domain name and optionally set optimizeFor. It does not explicitly name alternatives or state when not to use the tool, but the purpose is specific enough that an agent can infer this is the first step before registering a domain. The lack of explicit alternative routing prevents a 5.

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