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

Annotations already say read-only, idempotent, non-destructive, but the description adds material context the annotations cannot: $0.001 USDC per call via x402, errors are free, invalid input returns 400 and is never charged, unavailable values come back null with a note rather than fabricated, and every response carries a disclaimer field. That is exactly the payment/auth and failure-mode information an agent needs before calling.

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?

Dense but front-loaded with the highest-stakes fact (cost per call), then resolution rules, then error/null semantics. One long semicolon-chained block is efficient though it sacrifices some scannability.

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, the description still discloses the key return fields (forwardVerified, disclaimer, null-with-note for unobtainable values) plus the pricing and 400 failure path. An agent has everything needed to decide to call it, pay for it, and interpret the result.

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 baseline would be 3, but the description adds meaning beyond the schema by binding each input form to an outcome (base.eth → Basenames registry, .eth → ENS mainnet resolver, 0x → reverse lookup returning forwardVerified). The single parameter is thus semantically richer than its schema line.

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 (name resolution) plus the exact resources and sources: *.base.eth via the Basenames registry on Base, *.eth via the ENS Universal Resolver on mainnet, and reverse lookup for a 0x address. This is clearly distinguishable from siblings like base_token_info or base_wallet_balances, which deal with tokens and balances rather than name resolution.

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?

It gives input-driven routing ('name.base.eth, name.eth, or 0x address for reverse lookup'), which tells the agent exactly which input selects which behavior. It does not name an alternative tool or state when not to use this one, so it falls short of a 5.

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