check_domain

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

No annotations are provided, so the description carries the behavioral disclosure burden. It discloses some behavior via the Args (use_cache = TTL cache with 5-minute default, include_raw = verbose payload) and Returns (status, registrar, dates, nameservers), which adds context. However, it does not disclose network latency considerations, rate-limit behavior, or what happens with unsupported TLDs, which could matter for a network-dependent checking tool with sibling list_supported_tlds.

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 reasonably concise and well-structured with Args/Returns sections. The Args section repeats parameter names that already exist in the schema, but adds meaningful commentary with examples and defaults. Each line earns its place; no filler. Could be slightly tighter but is efficient overall.

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 this is a network-dependent tool with a an output schema, the description is decently complete: it covers inputs, outputs, and cache behavior. However, it lacks guidance on edge cases like invalid domains, unsupported TLDs (despite a sibling list_supported_tlds suggesting TLD awareness matters), and expected behavior when RDAP/WHOIS fails. The absence of annotations increases the burden the description must carry, and this falls slightly short for a tool with real-world network dependencies.

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 0%, so the description must compensate for all parameter meaning. It does explain each parameter: domain (with example including internationalized 'bücher.de'), include_raw (verbose), use_cache (in-memory TTL cache, 5 min default). While this adds value beyond the bare schema, the explanation is light — it doesn't detail return value structure for include_raw or how cache invalidation works, though the output schema partially mitigates this.

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 checks if a single domain is available or registered, using a specific verb ('Check') with a resource ('single domain'). It distinguishes itself from the sibling check_domains (batch) by explicitly noting 'a single domain', providing differentiation. The Args section and Returns section add clarity to the purpose.

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 mentions 'single domain' which implicitly differentiates from check_domains (batch), suggesting when to use this vs the batch tool. However, it doesn't explicitly state when NOT to use it or call out alternatives by name like domain_info or list_supported_tlds. Usage guidance is implied through the 'single domain' keyword rather than being explicit about exclusions or alternatives.

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