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

With no annotations, the description carries the full burden and does real work: it discloses the Ethereum mainnet-only registry scope, that wildcard and offchain resolvers are not followed, that reverse results are returned only if forward-verified, and that each call costs $0.005 USDC on Base or Solana via x402. It omits rate limits, latency, and what each resolver/record field means, so it is strong but not exhaustive.

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 the usage trigger, then Input, Output, scope caveats, an example, and price in a compact telegraphic format with no filler. It is somewhat over-packed into run-on colon-separated fragments, which slightly hurts readability but wastes almost nothing.

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, and the description does compensate by enumerating the returned fields for both modes, including contenthash and matchesExpected. The one real gap is that zero parameters are marked required, so the behavior when neither name nor address is supplied is never stated.

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 schema already explains name normalization, the 400-before-payment behavior, and that address alone means reverse while address plus name yields matchesExpected. The description restates the two inputs and adds the forward-verification rule for reverse results, but contributes little parameter-level meaning beyond the schema.

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 specific verbs and resources: forward resolution of an ENS name to address plus profile records, and reverse lookup of address to a verified primary name. The dual-mode framing is precise enough to call correctly, but the description never distinguishes itself from the sibling domain_lookup, so an agent cannot tell which of the two to pick from names alone.

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 concrete situational triggers that most agents would otherwise miss: 'when an agent must send funds to an ENS name or label a wallet', which implicitly selects the resolve vs reverse modes. It stops short of exclusions or naming an alternative, and the combined name+address verification mode is only revealed later in the output section rather than in the usage guidance.

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