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

Discloses data provenance ('read live from Ethereum mainnet'), full pricing model ('$0.002/call via x402 USDC or a card key, first 25 free; failed calls free'), and explicitly reconciles the readOnlyHint=false annotation by explaining it is a read/compute-only tool charged per call. This is exactly the kind of context annotations cannot convey.

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 purpose and an example, followed by actionable pricing and behavior notes. Every sentence earns its place, though the pricing/annotation sentence is somewhat dense and could be slightly tighter.

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 only one parameter, no output schema, and existing annotations, the description still covers return content (address/avatar or primary ENS name), data source, and cost model. Nothing an agent needs 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% and the single parameter is fully documented in the schema itself ('An ENS name such as vitalik.eth, or an address (0x...) for reverse lookup'). The description's example and dual-usage note add marginal value over the schema, so the baseline of 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 / address) and covers both directions: forward resolution (vitalik.eth → address and avatar) and reverse resolution (address → primary ENS name). An agent can immediately tell what this does versus the network-specific sibling tools like eth_balance or wallet.

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 clear when-to-use context: 'turn a human-readable name into a payable address' or 'show a readable name for a counterparty address.' This is concrete intent guidance, though it does not name a specific sibling alternative or state 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.