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

Adds far more than the annotations: malformed addresses return 400 uncharged, failed calls are free, first 25 free, $0.003/call via x402 USDC or card key. Critically, it reconciles the surprising readOnlyHint=false by explaining why (per-call billing), which is exactly the context an agent needs to trust the annotation rather than be confused by it.

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?

Front-loads capability, then alternatives, then error/pricing terms, all in four tight sentences. The embedded example address is long but pays for itself as a copy-pasteable format cue.

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?

No output schema exists, so the description correctly states both return units (wei and ETH). Input format, error handling, and billing quirks are all covered; nothing an agent needs to invoke it correctly is missing.

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% and there is one parameter, so the baseline is 3, but the description adds the accepted format ('any 0x address'), a concrete example value, and the failure behavior for malformed input, which the schema does not convey.

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 (read), resource (native ETH balance), chain (Base), block scope (latest), and output units (wei and ETH). It is immediately distinguishable from base_token_balance and wallet_portfolio, both of which it names.

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?

Gives the concrete use case ('check whether a wallet can pay gas or a transfer') and explicitly routes to siblings for the two nearest alternatives: base_token_balance for ERC-20 and wallet_portfolio for all holdings.

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