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

There are no annotations, so the description carries the full burden. It does disclose the per-call cost of 0.002 USDC over x402 and the return contents (wei, ETH, block height). It does not mention that the call is read-only, whether it needs a payment wallet or auth setup, or how payment failures behave.

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 sentences, front-loaded with purpose and return contents. The middle sentence is redundant 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?

There is no output schema, and the description partly compensates by listing the returned fields. Gaps remain: the meaning and defaults of chain, payment prerequisites, and guidance on choosing among the closely related balance siblings.

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 nominally 100%, but the schema descriptions are only examples. The description says "on Base" yet does not explain the optional chain parameter: whether other chains are accepted or what the default is. The description adds little beyond the schema.

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 description states the resource precisely: the native ETH balance on Base for any address, returned in wei and ETH with block height. "Native ETH" implicitly separates it from evm_token_balance and evm_portfolio, but neither sibling is named.

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 it to read a wallet balance" restates the purpose and offers no real guidance. It never says to use evm_token_balance for ERC-20 balances or evm_portfolio for a full holdings view, which is where an agent is most likely to choose wrong.

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