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

Annotations cover readOnly/openWorld/destructive, and the description adds substantial context beyond them: per-call x402 pricing ($0.002 USDC), errors are free, invalid input returns 400 and is never charged, data is read live via Multicall3 and cached 10 s. This is rich behavioral disclosure an agent needs before paying.

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?

Dense but front-loaded: pricing/error terms lead, then scope, then data source and failure mode. Every sentence carries information, though the single paragraph is somewhat packed.

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, yet the description fully enumerates the return contents (balances, nonce, account type, USD total) plus the data source, cache window, default address, and error semantics. An agent has everything needed to call and interpret it.

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%, so all three params are already documented. The description restates that `tokens` are read on-chain (symbol/name/decimals) and that includeZero lists zero-balance tokens, adding only marginal value over the schema. Baseline 3 applies.

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 (fetch balances of one address on Base mainnet) and enumerates exactly what is returned: native ETH, named tokens, up to 10 extra ERC-20s, nonce, account type, USD total. It is clearly distinguishable from siblings like base_token_info (token metadata) and base_gas_price.

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?

Explains when to use includeZero=true (list zero-balance well-known tokens) and the `tokens` param (up to 10 extras), plus that all params are optional with a default address. Lacks explicit routing against alternatives, but the context for invoking it correctly is clear.

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