dns_lookup

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

No annotations are provided, so the description carries full burden. It states 'Read-only; requires no API key or authentication; subject to rate limiting' and describes the return format (text report with status, KPI, issues, actions). This provides good behavioral context, though specific rate limits or error handling are not mentioned.

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 concise (three sentences) and well-structured: first sentence states purpose and capabilities, second provides usage guidance, third covers behavioral traits and return format. Every sentence adds essential information.

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?

The tool has one parameter and no output schema, but the description sufficiently explains that it returns a text report with status, KPI, issues, and actions. It covers the main behavioral aspects (read-only, no auth, rate limiting). However, it does not describe error handling or what happens for invalid domains.

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% with a clear description for the 'domain' parameter. The description adds value by explaining what the tool does with the domain (querying specific record types and validating email records), which enriches the parameter meaning beyond the schema alone.

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 specifies that the tool queries DNS records (A, AAAA, MX, TXT, NS, SOA, CAA) and validates email-related records, including DNSSEC and SPF/DMARC. It distinguishes itself from sibling tools like dns_propagation and email_auth by stating its unique scope.

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?

Provides explicit guidance: 'Use this for a single authoritative answer about one domain. Use dns_propagation instead when you need to compare answers across multiple global resolvers... or email_auth for a full SPF/DKIM/DMARC deliverability assessment.' This clearly tells the agent when to choose this tool over alternatives.

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