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

Goes well beyond the readOnly/openWorld annotations by disclosing the transport ('read over public RPC'), the cost model ($0.002 USDC per call), the payment rail (x402 on Base/Solana/Arc), and crucially that failed calls are not charged. This is exactly the kind of operational context annotations cannot carry.

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 returned fields and chain list, followed by chain-specific ENS behavior and then pricing. Three dense sentences with no filler; the pricing sentence earns its place because it affects invocation decisions.

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 an output schema present, return values need no explanation, and annotations cover safety; the description still supplies cost, transport, chain scope, and account-type nuance. Minor gaps remain around latency/rate limits and explicit sibling disambiguation, but nothing an agent needs to call it 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 the baseline is 3, but the description adds meaning the schema lacks: it characterizes what an address can be (wallet, contract, EIP-7702 delegated wallet with its delegate) and notes the ENS name is returned only on Ethereum when it resolves back. That enriches interpretation of the single address parameter.

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?

The description states a specific resource and the exact fields returned (native balance, nonce, account type, ENS primary name) plus the supported chains, so overlap with generic 'balance' tools is minimized. It does not, however, name or differentiate itself from close siblings like evm_balance, evm_wallet, or rpc_evm.

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?

Usage is implied by the scope of what is returned, and the chain default (Base) is stated, but there is no explicit when-to-use guidance or routing to alternatives such as evm_balance or evm_wallet. The agent must infer the choice from the field list alone.

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