DNS lookup

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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the 'Read-only' line is largely redundant. However, the warning that probed-site text (titles, headers, DNS records, file contents) is untrusted data rather than instructions is genuinely valuable prompt-injection context that annotations do not convey.

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?

Three tight sentences: purpose and scope first, then routing guidance, then the trust warning. Every sentence carries information and nothing is 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 could say a bit more about return shape (e.g. per-type record sets, TTLs, resolver errors), but the record-type list and resolver note make the output sufficiently predictable for a 2-parameter read 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 both parameters are already documented in the schema, including the record-type enum and the example name format. The description's enumeration of record types mirrors the schema enum and adds no new syntax or format detail, 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 (looks up) and resource (DNS records), enumerates the supported record types, and specifies the resolver used. It clearly distinguishes itself from mail_auth, the sibling that handles SPF/DKIM/DMARC.

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 explicit use cases (check propagation, verify records after a change, investigate mail routing) and names the alternative for a related but distinct task: 'For SPF/DKIM/DMARC use mail_auth instead, which interprets them.' This is textbook when-to-use plus when-to-use-something-else.

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