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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds no behavioral context beyond the schema's own 1-5 domain limit — nothing about failure handling for unresolvable domains, resolution cost, or whether results are cached. It contributes essentially nothing an agent can't get from the structured fields.

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?

A single dense sentence with no filler, and the domain count is placed at the end where it is easily found. It is jargon-heavy but nothing is wasted.

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, listing the returned record types (MX, SPF, DMARC pct/rua, A/AAAA/NS/TXT) is genuinely useful and is the description's main contribution. Still, for a tool that fans out DNS lookups across multiple record types, the absence of any usage or failure-behavior context leaves it only minimally complete.

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 0%, so the description carries the parameter burden, and 'for 1-5 domains' usefully restates the accepted cardinality. However, it says nothing about element format (bare domain vs. URL vs. subdomain), and the maxItems=5 constraint is already in the schema, so the addition is marginal.

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 enumerates the data the tool collects (MX provider, SPF qualifiers, DMARC policy/pct/rua, A/AAAA/NS/TXT checks) but never states a verb or framing like 'look up' or 'check email security DNS records for domains'. It reads as a return-value list rather than a purpose statement, and it does not distinguish itself from siblings such as tech_stack that also probe a domain.

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?

There is no when-to-use guidance, no mention of prerequisites (e.g., domain must be resolvable), and no routing to or away from siblings like tech_stack or domain_report. Usage is only weakly implied by the resource being a domain.

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