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

With no annotations, the description carries the full burden, and it does disclose two non-obvious traits: the operation costs $0.001 USDC on Base via x402 (a payment requirement an agent must know), and the return is an exact raw integer (not decimal-adjusted). It omits read-only confirmation, error behavior for non-contract addresses, and any rate limits.

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?

Three dense sentences, front-loaded with the resource and mechanism, then the return shape, then the cost. Every sentence adds information; nothing is padding.

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 explains the return ('exact raw integer balance') and covers payment, chains, and token coverage. The only real gap is that it does not tell the agent to divide by the token's decimals to get a human-readable amount, a caveat worth flagging for a raw-integer return.

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 description coverage is 0%, so the description must compensate, and it maps all three parameters to meaning: 'wallet' (address), 'token contract' (contract), and 'Base or Ethereum' (network). It does not restate the 0x-address format or default network, which the schema's pattern and enum already convey.

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+resource (ERC-20 token balance), the exact mechanism (balanceOf eth_call), the scope (any EVM wallet and token contract), and the supported chains (Base or Ethereum). This cleanly separates it from siblings like chain-native-balance, chain-erc20-allowance, and chain-live-balance without opening any schema.

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 description implies when it applies ('for USDC, USDT, DAI and arbitrary ERC-20 tokens') but never names an alternative or an exclusion — it does not say to use chain-native-balance for ETH or chain-erc20-allowance for approvals. Usage is inferable rather than stated.

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