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

With no annotations, the description carries the full behavioral burden. It does disclose meaningful context beyond the schema — the paid call model ($0.001 per call via x402, USDC on Base) — but says nothing about latency, timeouts, caching, or what a failed/non-resolving domain returns.

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?

Two short sentences, front-loaded with the capability and followed by the cost. The only waste is 'Input: d', which merely restates the schema field.

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?

No output schema exists, but the description tells the agent what data comes back (resolution status plus A, MX and NS records), and pricing is covered. A one-parameter read-only lookup is adequately specified, though failure-mode behavior is not addressed.

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% (the single 'd' parameter is documented as 'Domain name, e.g. example.com'), so the schema does the heavy lifting. The description's 'Input: d' adds no meaning beyond it — baseline 3.

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 (DNS check) and resource (a domain), and enumerates the exact lookups performed (resolution, A, MX, NS). That would let an agent distinguish it from siblings like validate_email, though it never names an alternative explicitly, so it stops short of a 5.

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 or when-not-to-use guidance, no prerequisites, and no mention of alternatives such as validate_email. Usage is only implied by the tool name and description.

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