dns_lookup

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

Annotations already declare readOnlyHint and openWorldHint, and the description adds behavioral specifics by stating that all listed record types are returned unless the user filters with 'type.' This tells the agent what to expect from the call, and does not contradict the annotations.

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 two-sentence description is front-loaded with the primary action and wastes no words. Every sentence carries distinct information: the first covers the operation and return set, the second covers the optional filter.

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 2-parameter, read-only lookup tool with no output schema, the description covers the core behavior and output scope. It does not mention failure modes or behavior on invalid 'type' values, but these are minor for an agent deciding how to invoke the 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%: both 'domain' and 'type' are documented in the schema, including the allowed record types. The description's phrase 'Optionally filter by record type' merely echoes the schema, so it adds no new semantic information; baseline 3 is appropriate.

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 opens with a specific verb and resource, 'Query DNS records for a domain,' and enumerates the record types returned (A, AAAA, MX, TXT, CNAME, NS, SOA, SRV, CAA, PTR). This clearly conveys the tool's function, though it does not explicitly contrast with sibling tools like dns_propagation, so it earns a 4 rather than a 5 for differentiation.

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 gives no guidance on when to choose dns_lookup over related siblings such as whois_lookup or dns_propagation. The only usage note is 'Optionally filter by record type,' which addresses parameter selection, not tool selection, so the dimension remains unaddressed.

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