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

Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond them by disclosing the execution model (one Multicall3 call per chain), a real coverage limitation (only listed tokens checked, not every token held), and a cost/billing model ($0.003 USDC via x402 per successful call, failures not charged). This is exactly the behavioral context an agent needs before invoking a paid tool.

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?

A single dense paragraph that is front-loaded with purpose, then coverage caveats, then pricing. Every sentence carries information (scope, limitation, cost) with no filler, though it is longer than strictly minimal and lacks visual structure.

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?

An output schema exists, so return-value explanation is unnecessary. Combined with annotations covering the safety profile, the description supplies chains, token coverage, omissions, per-chain execution, and the payment model — everything an agent needs to call this correctly.

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% and both parameters are documented in the schema, so the baseline is 3. The description restates the chain options and default and clarifies that chain=all queries every chain, but adds little syntax or semantics beyond what the schema already provides.

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: retrieves native balance plus named tokens (USDC, USDT, EURC, DAI, WETH, cbBTC, WBTC) for an EVM address, with USD values. The wallet-level aggregate framing implicitly distinguishes it from evm_balance (native only) and evm_token (single token), and 'EVM address' separates it from solana_wallet.

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?

Provides useful context — Base is the default chain, chain=all spans every chain, and zero balances are omitted — but never states when to prefer this over evm_balance or evm_token. Usage is implied rather than routed, with no explicit when-not guidance.

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