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

With no annotations, the description carries the full burden and does well: it discloses per-call pricing ($0.003 USDC), the default chain (base), the supported chain set, and the 10-address cap on custom tokens. It omits failure behavior (unknown chain, malformed address) and whether nonce/is_contract incur extra work, which keeps it from a 5.

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?

One dense paragraph, front-loaded with the trigger and payout, and every clause carries information (assets, limits, chains, price, related tool). The parenthetical '(+ up to 10 custom ERC20 addresses comma-separated)' is awkwardly stacked and could be split for readability, but nothing is wasted.

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?

There is no output schema, so the description correctly takes on the return contract by naming the balance set plus nonce and is_contract. Combined with pricing, chain defaults, and token limits, an agent has enough to invoke it correctly; only address formatting and error semantics are 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 0%, so the description must compensate, and it does for two of three parameters: chain is enumerated with its default, and tokens is defined as comma-separated custom ERC20 addresses capped at 10. The address parameter's expected format (0x-prefixed hex, EVM-only) is never stated, leaving one gap.

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 and resource ('an EVM wallet's balances in one call') and enumerates exactly what comes back: native ETH/POL, six named stablecoins/tokens, nonce, and is_contract. The 'in one call' phrasing implicitly separates it from the single-asset siblings chain_balance and chain_erc20_balance, and it names a related tool (token_check) for the adjacent job.

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?

Opens with an explicit trigger ('Use this when you need an EVM wallet's balances in one call') and adds a cross-sell pointer to /token-check with its price for the vet-before-transfer case. It never states when NOT to use it, so an agent can't tell from this text whether a single-token lookup should go to chain_erc20_balance instead.

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