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

With no annotations, the description carries the full behavioral burden and does disclose key traits: data is read live from public RPC and, importantly, the call is paid (0.01 USDC on Base via x402, 12 sats Cashu NUT-24, or 12 sats L402). It does not cover rate limits or error behavior, but the payment requirement is a significant disclosure most definitions omit.

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 well front-loaded: scope and return shape first, then parameter guidance, then the read/payment facts. Each sentence adds information; slightly long but no filler.

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?

For a 3-param tool with no annotations and no output schema, the description covers scope, chain enumeration, token syntax and defaults, data source, and cost. Remaining gaps (address format, chain default, return structure) are minor but real given zero structured support.

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. It does explain tokens= (symbols like USDC/USDT/DAI/WETH or contract addresses, comma-separated, with a documented default) and implies the chain values via the enumerated list, but the address parameter and the chain default are never described.

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 ('Wallet balance on an EVM chain') and enumerates the supported chains plus the fact that it returns native coin and ERC-20 balances. It is clearly distinguishable from evm_gas/evm_tx/evm_token by resource, though it never names those siblings explicitly.

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?

Usage context is implied by the resource and the token-symbol guidance, but there is no explicit when-to-use statement and no exclusions or named alternatives among the evm_* siblings. An agent must infer that this is the balance-lookup tool versus evm_token or evm_tx.

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