check_availability

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

With no annotations, the description carries the full burden. It discloses that no API key is required, defines the full return shape, enumerates the possible reason values, and clarifies the detail field. It doesn't mention rate limits or edge cases, but for a simple check this is solid coverage.

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 tight sentences: the first states the action and timing, the second covers auth and the exact return contract. No filler, no repetition of schema. The key scoping context ('before claiming it') is front-loaded.

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?

There is no output schema or annotations, so the description must directly compensate. It provides the complete return structure, explains every reason value, and includes domaine-related fields. For an agent that needs to decide, call, and parse the result, this is sufficient.

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?

Input schema already covers both parameters with 100% description coverage, so a baseline score of 3 is appropriate. The description adds no input-specific semantics beyond the return shape mentioning 'domain' and 'fqdn'; it doesn't elaborate on label constraints or domain nuance that the schema already handles.

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?

Description uses a specific verb ('check') and resource ('subdomain label'), and states the precise predicate (whether free) while explicitly tying to claim action. It clearly reads as a pre-check for claim_domain and is not confusable with listing, creating, or deleting domains.

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 'before claiming it' gives a clear usage context relative to claim_domain, but it does not explicitly name alternatives or state when not to use the tool. This is contextual but relies on the agent to infer the connection to claim_domain.

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