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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the description does not need to re-prove safety, yet it adds real value beyond them: live mainnet reads, a price of $0.002/call via x402 USDC or card key, first 25 free, and failed calls free. The one behavioral gap is what happens on an unresolved or malformed name, which is not stated.

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 two resolution directions, then usage, then pricing and safety. Every sentence carries information, though the pricing and free-tier clauses add bulk that could be tightened without losing meaning.

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 correctly names what comes back (wallet address plus avatar, or the primary ENS name), which is the key completeness requirement for a single-parameter read tool. Return-shape details such as null/not-found handling are the only missing piece.

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?

There is one required parameter with 100% schema coverage, and the schema already explains that 'name' accepts either an ENS name or a 0x address for reverse lookup. The description's 'Example: name=vitalik.eth' and the address-to-name sentence restate rather than extend that, so 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 (resolve/look up) and resource (ENS name), covering both forward resolution to address+avatar and reverse resolution to primary name, and names the chain (Ethereum mainnet). It is clearly distinguishable from the sibling address/hash utilities like evm_checksum and eth_balance.

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 when-to-use guidance twice: 'turn a human-readable name into a payable address' and 'show a readable name for a counterparty address.' It does not name an alternative tool or state when not to use it, but the intent is unambiguous from the description alone.

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