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

Annotations already declare read-only and open-world behavior, so the description focuses on what annotations cannot say: answers come from public resolvers, private/internal answers are deliberately filtered, and the enum of record types. It does not mention caching, resolver fallback behavior, or failure modes (NXDOMAIN vs no records of a type), which keeps it below a 5.

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 compact sentences: capability and record types first, then the important behavioral caveat (filtered private answers) and cost. No filler, nothing buried.

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 does say what is returned (each record type with its values), which is the key missing structured information. For a single-parameter read-only lookup this is nearly complete; only edge-case behavior (no records found, invalid domain) is unaddressed.

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 and the schema already describes it at 100% coverage ('Domain or https URL'). The description adds no format details, e.g. whether a bare hostname, subdomain, or URL with path is accepted, so it matches the schema rather than extending it.

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 (look up) and resource (public DNS records) and enumerates the record types covered plus the resolution path (public resolvers). No sibling tool in the list deals with DNS, so no differentiation is required; the purpose is unambiguous.

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?

Usage is implied by the scope ('public records through public resolvers') and the note that private answers are filtered out, but there is no explicit when-to-use or when-not-to-use guidance, nor any named alternative for private/internal resolution.

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