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

With no annotations, the description carries the full burden and delivers unusual value: the underlying method (eth_getBalance), the absence of rate limits and API keys, the flat pricing, and the x402/USDC payment requirement. It does not cover failure modes (invalid address, unsupported chain) or whether the returned value is wei/hex, so it falls 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?

Three short, front-loaded sentences with no filler; capability first, then operational constraints, then the underlying RPC method and cost. Every clause carries information.

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 two-parameter read tool with a fully documented schema, the description covers capability, chains, and the payment/access model. The only meaningful omission is the shape of the returned balance (wei vs. decimal string), which matters since there is no output schema.

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 description coverage is 100% and both parameters are documented in the schema, so the baseline is 3. The description's chain list duplicates the enum-style values already given in the chain property and adds no format or syntax detail beyond it.

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 (native coin balance for any address) and enumerates the supported chains, making it clearly distinct from the sibling evm_erc20_balance and evm_token_info. An agent can route to it without opening the 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?

The description establishes context (multi-chain native balance, no API key, flat price) but never says when to prefer this over evm_erc20_balance, evm_portfolio, or evm_chains, nor what conditions exclude it. Usage is implied by the resource name rather than stated.

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