dns_lookup

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

With no annotations, the description carries the disclosure burden and does well: it states the return shape ('records object with array per type'), the default type, supported types, cost, and p99 latency. It omits auth requirements, broader rate-limit behavior, and failure modes, so it is not fully complete.

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?

Front-loads purpose and supported record types, then adds operational details—return shape, cost, latency—without filler. The few repeated schema details are useful for quick scanning and do not make it verbose.

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 low-complexity read tool with no output schema, the description supplies the key return shape, default behavior, supported types, cost, and latency. Exact response field structure and error behavior are not detailed, but the definition is sufficient for selection and invocation.

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%, and the schema already documents both 'domain' and 'types' with the enum and default. The description reinforces the default and supported types but adds no syntax or semantic 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: 'Resolve DNS records for any domain.' It enumerates the supported DNS record types, making its domain-record focus distinct from adjacent tools like whois, ssl_check, and domain_check.

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 positive triggers: verify mail server setup with MX, check domain ownership with TXT, and debug DNS propagation. It does not provide when-not-use guidance or name alternative sibling tools such as whois or domain_check.

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