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

Annotations only declare readOnly and openWorld; the description adds genuinely non-obvious behavior: cost ($0.002 USDC per successful call), payment rails (x402 on Base, Solana or Arc), and the credit that failed calls are not charged. It also discloses the non-recursive lookup behavior, which affects how an agent should interpret an empty response.

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?

Purpose is front-loaded in the first clause, followed by record-type detail, the scope caveat, and the pricing note; there is little waste. The parenthetical payment-rail enumeration is slightly heavy but is load-bearing for cost expectations.

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?

Output schema covers return values and annotations cover safety, so the description's remaining burden is scope and cost — both are addressed, including the inheritance caveat and per-call billing. Nothing an agent needs to call this correctly is missing.

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% and the single `domain` parameter is fully documented in the schema with an example. The description adds no syntax, format, or validation detail beyond that, 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 ('Lists the CAA ... records published on a domain') and enumerates exactly which record types are returned (issue, issuewild, iodef). The CAA specificity inherently separates it from the generic security_dns_records sibling, so an agent can route without opening the schema.

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?

Explicitly names the scope boundary: 'Shows the records on the exact name only; CAA is inherited from parent domains when a name has none, which this tool does not walk.' That tells the agent when this tool will return empty results and that parent-domain resolution is out of scope. It does not name a sibling to use instead for the inheritance case, which keeps it below a 5.

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