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

With no annotations, the description carries real weight and does so: it discloses the resolver used (universal resolver) and the payment requirement ($0.005 USDC on Base via x402), which is critical for an agent to avoid unexpected failure. It omits behavior on unresolvable names and any partial-result semantics.

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?

One dense sentence plus two short supporting sentences; the resolution direction and the returned record types lead, and the cost/auth note trails. No filler and nothing buried.

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?

Without an output schema or annotations, the description still tells the agent what comes back (address, avatar, description, url, Twitter, GitHub) and what it costs. Missing are failure/empty-result behavior and whether supplying both parameters is an error — meaningful for a paid, zero-required-param tool.

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%, so both parameters are documented at the structured level. The description adds value by framing them as alternatives — name for forward resolution, address for reverse lookup — and by enumerating the record types returned, which the schema does not convey.

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?

Names a specific verb (resolve) and resource (ENS name), covering both directions: forward resolution to address plus profile records, and reverse lookup from address to primary name. The `eth_` prefix and ENS specificity clearly separate it from `base_resolve_basename` among the siblings.

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 states the two usage modes with example inputs ("vitalik.eth" vs "pass an address instead"), giving clear context for when each parameter applies. It stops short of naming the basename sibling as the alternative for Base names, leaving that distinction to the naming convention.

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