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

Describes live on-chain read and the exact cost ($0.001 USDC on Base, x402). However, it contradicts the annotations: the description says it's a read of a balance, yet has readOnlyHint=false, and it mentions a payment requirement while annotations declare non-idempotent, open-world behavior. It doesn't explain what happens on failed call or payment failure. The annotations mislead here.

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 concise sentences: first the payload, then usage, then cost/payment. It is front-loaded and each sentence adds distinct value.

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?

Given only 2 params and no output schema, the description provides enough context for an agent to call it correctly: on-chain read, cost, payment chain. It could mention rate limits or failure behavior, but is effectively complete for a lightweight read tool.

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%, both parameters are documented with types and formats. The description does not add format or constraint details beyond the schema, so baseline 3 is suitable.

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 and resource: reads the ERC-20 token balance of a wallet on Optimism, and enumerates the returned fields (raw amount, decimals, symbol, human-readable amount). It is clearly distinguishable from sibling op_token_info (metadata) and op_balance (native ETH).

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 a concrete usage scenario: check holdings before a transfer, payment or trade. It does not explicitly name alternatives such as wallet_portfolio or explain when not to use it, but the use case is clear.

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