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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, providing a strong safety baseline. The description adds 'Free public API', which signals no authentication requirement or potential rate limits, giving extra context beyond the annotations. It does not describe return format, but that is not critical for a simple read operation.

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 two short sentences, front-loaded with the primary action. 'Free public API' is a minor addition, but every other word earns its place. It is highly concise and well-structured.

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 simple tool with two parameters and no output schema, the description is sufficiently complete. It specifies the resource (DNS records), scope (any domain), and supported record types. The only minor gap is the lack of detail about response format or error handling, but that is not necessary given the tool's simplicity and the annotations covering safety.

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 coverage is 100%—both 'domain' and 'type' have detailed descriptions in the schema. The description's mention of record types mirrors the enum in the schema without adding new meaning. Therefore, it meets the baseline of 3 but does not exceed 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?

The description clearly states the tool looks up DNS records and lists the specific record types (A, AAAA, CNAME, MX, TXT, NS, SOA) for any domain. This distinguishes it from sibling tools that focus on single record types like CNAME or TXT lookups, making the purpose 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?

The description implies general DNS lookup usage by enumerating record types and stating 'any domain'. It does not explicitly mention alternatives like specific record lookup tools, but the context is clear enough for an agent to infer when to use this tool versus siblings. No misleading guidance is present.

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