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

With no annotations, the description carries the full burden and does so: it discloses partial-failure handling (failed chains appear in chainsFailed), settlement behavior (only successful reads are charged; invalid input, not-found and upstream errors cancel settlement), and the exact price ($0.005 USDC on Base). This is exactly the payment and error semantics an agent needs before invoking.

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 payoff (one call vs 21) and then failure and pricing semantics; almost nothing is wasted. The closing parenthetical price could arguably be folded in earlier, keeping it from a 5.

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?

No output schema exists, and the description compensates by stating what comes back (per-chain native/USDC/USDT balances, a total stablecoin figure, and chainsFailed). Combined with the payment semantics, an agent has everything needed to call it and interpret the result.

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 already 100%, so the baseline is 3; the description adds meaning by clarifying that chains accepts a subset with all seven as default and by tying paymentSignature to the settlement behavior described above. It does not add syntax detail beyond the schema example, so it stays below 5.

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 gives a specific verb and resource — returns native coin, USDC and USDT balances across seven named chains plus a total stablecoin USD figure — and explicitly frames it as a batch replacement for 21 separate reads, which differentiates it from the sibling single-chain tools (chain_native_balance, chain_token_balance).

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?

'Instead of 21 separate reads' clearly signals when to prefer this over the per-chain siblings, and the 'or a chains subset' phrasing tells the agent how to narrow scope when full coverage isn't needed. It stops short of naming the alternative tools explicitly or stating exclusions, so it is not a 5.

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