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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds a genuine behavioral trait beyond that: only an unambiguous WHOIS status is reported as available/registered, and an inconclusive lookup is surfaced as such rather than being guessed. That uncertainty-handling behavior is not derivable from the schema or annotations.

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 front-loaded sentences with no filler; the mechanism and the scope constraint come first, followed by the reporting behavior. Slightly dense but every clause carries information.

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 one-parameter, read-only lookup with no output schema, the description covers what the tool does, what it accepts, and how ambiguous results are reported. Only the absence of any explicit routing against sibling domain tools keeps it from being fully complete.

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% and the single 'domain' parameter is already documented with a format example ('z. B. example.de'). The description adds no syntax or validation detail beyond that, so the baseline 3 applies.

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?

States a specific verb and resource ('Prüft, ob eine beliebige Domain zur Registrierung verfügbar ist') and pins down the mechanism (WHOIS-Lookup). The parenthetical clarifying that it is 'nicht auf eigene Domains beschränkt' implicitly distinguishes it from sibling get_domains, though no sibling is named explicitly.

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 scope note tells the agent this works for arbitrary domains, which is useful context, but there is no explicit statement of when to prefer this over prepare_domain_order or suggest_domain_alternatives. Usage is implied rather than directed.

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