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

With no annotations, the description carries the full burden and does disclose key traits: the $0.005 cost paid over x402 with USDC, and the internal mechanics (eth_getBalance + eth_call). It omits error/edge behavior for invalid token addresses and any rate limits, but the payment requirement is meaningful behavioral context rarely found elsewhere.

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 tightly packed sentences: what it returns, why it beats per-token calls, its internal method, and its cost. Front-loaded with the capability, no filler, every clause earns its place.

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 does describe the return shape at a useful level (balances with symbol and decimals already applied). It does not clarify whether the native balance is returned separately from the token array or the exact response structure, leaving a small gap for a tool with this many tokens returned.

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 100%, so the schema already documents address, chain options, and the up-to-20 token array. The description reinforces 'on one chain' and 'every token you list' but adds no format or constraint detail beyond the schema. Baseline 3 is appropriate.

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: native balance plus balances of listed tokens on one chain in a single call. The phrase 'One request instead of one per token' implicitly distinguishes it from the per-token siblings like evm_balance and evm_erc20_balance. An agent can identify what this tool uniquely does 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?

Clearly frames the usage context: batching many token lookups into one paid call rather than one per token, which implies when it is preferred. It does not name alternative tools or state explicit when-not conditions (e.g., use evm_balance for native-only), so it falls short of 5.

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