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

Goes well past the readOnly/openWorld/idempotent annotations: discloses live resolution via the ENS Universal Resolver with CCIP-read, a per-call price ($0.001 USDC on Base), the x402 flow, and concretely what an unpaid call returns plus the exact retry mechanism (params._meta["x402/payment"]).

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-loaded with the primary name→records behavior, followed by the address mode and then payment mechanics. It is dense with parentheticals and a raw HTTP endpoint, but nearly every clause carries operational value.

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 enumerates the returned fields (address records, resolver, url/avatar/com.twitter/description, reverse_matches) and covers the payment failure path and HTTP equivalent. Nothing needed to call it 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%, so baseline is 3, but the description adds real meaning: name yields records plus reverse_matches, while address yields a forward-verified primary name across mainnet and Base/ENSIP-19. That explains the semantic difference between the two optional parameters, not just their syntax.

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 (resolve) plus both directions (name→address records, address→primary name) and names the namespaces (ENS, Basename, ENSIP-19). An agent can distinguish it from sibling lookups like domain_check or address_info from the description 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?

The 'Or pass address= for its forward-verified primary name' clause makes the two usage modes explicit, so an agent knows which parameter selects which behavior. It stops short of naming alternatives (e.g., address_info, domain_check) or stating when not to use it.

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