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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint, so safety is covered. The description adds genuinely non-derivable behavior: values come back both raw and formatted, and the result carries a signed receipt, which tells the agent the response is attestable.

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?

Two tight sentences with no filler. Asset scope and default are front-loaded, and the receipt note is appended only because it matters.

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?

An output schema exists, so return shape need not be explained, and the description covers chain, assets, encoding and the receipt. The one real hole is sibling disambiguation against erc20_balance.

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%, so both parameters (address, token_address) are already documented, including the USDC default. The description restates the default-token behavior but adds no format or constraint detail beyond the schema, so the 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: fetching native ETH and one ERC-20 (default USDC) balance for an address on Base. The scope (chain, asset types, default token) is concrete enough to distinguish it from generic balance readers, though it never names the near-identical sibling erc20_balance.

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?

No when-to-use, when-not-to-use, or prerequisite guidance. With erc20_balance in the sibling list, an agent has to guess which tool to pick for a single-token query versus this one; the description offers no routing rule.

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