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

With no annotations, the description carries the full behavioral burden and does so well: it declares the tool is read-only, external, operates over DNS/TCP, and never touches the target's application. It also enumerates the exact per-name-server verdicts, including the safe defaults and the edge case (NS resolving to an internal address), which is unusually complete.

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?

A single dense paragraph with the purpose front-loaded and supporting detail (RFC reference, verdict vocabulary, safety profile) ordered by usefulness. It is heavier than strictly minimal and leans on em-dashes, but nearly every clause contributes 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?

There is no output schema, so the description must explain the return values — and it enumerates every verdict with its meaning plus the attached record sample. Combined with the safety disclosure, nothing needed to interpret results is missing for a one-parameter 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?

Only one parameter, fully documented in the schema at 100% coverage ('Domain, e.g. example.com'). The description adds no syntax, format, or constraint detail beyond the schema, so the baseline of 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 — testing whether a domain's authoritative name servers allow an AXFR zone transfer — and immediately frames it as a misconfiguration check. An agent can distinguish this from dns_lookup or dns_propagation among the siblings without opening any schema.

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 situates the tool within DNS security auditing ('classic misconfiguration that leaks the entire zone') and defines what each outcome means, which tells the agent when the result is actionable. It does not explicitly name an alternative or state when NOT to use it, so it stops short of the top score.

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