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

Annotations already cover the safety profile (readOnly, idempotent, openWorld, non-destructive), so the description's job is to add behavioral context — which it does by enumerating return categories: per-server answers, disagreements, lame or silent servers, and CAA/ACME readiness. It doesn't discuss timeouts or rate limits against the many servers queried, but the added detail is substantive.

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 waste: the first front-loads the usage condition, the second enumerates the return content. Nothing is repeated or padded.

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?

With no output schema, the description carries the burden of describing returns and does so adequately, and annotations cover safety. Missing only edge-case behavior for large sweeps (timeouts, partial results), which is minor for this 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?

Schema description coverage is 100%, so the schema already documents names, types, and domain including defaults and the '@' apex convention. The description only alludes to 'each name and type you list' without adding format or constraint detail beyond the schema, 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 ('sweep a domain across its authoritative servers') and clarifies the output is a per-nameserver comparison, which implicitly separates it from single-query siblings like dig and trace. It stops short of naming any sibling explicitly, so an agent must infer the distinction.

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?

Gives an explicit trigger: 'Use after a zone change, when the person asks whether the authoritative servers agree.' That is clear context for selection. It does not state when not to use it or name an alternative (dig, check_domain), so it falls short of a 5.

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