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 the data source (public RPC), the price oracle (Chainlink), the hard cap of 10 tokens, and the pay-per-call cost ($0.002 USDC via x402), which is the key operational constraint. It does not cover error behavior for unsupported addresses or RPC failures, keeping it short of 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?

Content is front-loaded: what it returns comes first, then how to pass tokens, then when to use, then cost, then a sample response. It is dense in one paragraph but nearly every clause carries information; the example output is long yet justified because no output schema exists.

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?

Despite having no output schema and no annotations, the description supplies the return shape via a concrete JSON example, the payment model, the chain coverage, and the token limit. 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 chain enum, address, and the tokens list are already documented in the schema. The description adds only the concrete call syntax "tokens=0xA,0xB", which is a minor format hint rather than new semantic meaning. 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?

The opening sentence names the exact resource (wallet balance), the supported chains, and the returned contents (native coin with USD value plus up to 10 ERC20 balances). An agent can distinguish this from token_info, token_preflight and gas_estimate without opening any schema.

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?

"Use before funding, swapping or paying from a wallet" gives a concrete trigger context for calling it. It stops short of naming alternatives (e.g. token_info for token metadata, gas_estimate for fee planning) or stating when not to call it.

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