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

With no annotations, the description carries the full behavioral burden. It usefully discloses that the call runs on Base, resolves raw units/decimals/symbol on-chain, and costs 0.003 USDC via x402, but it omits error behavior, rate limits, and whether non-ERC20 tokens are rejected.

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?

The description is short and front-loads the core resource and return details. The sentence 'Use it to read a token balance' is largely redundant, but the pricing sentence earns its place.

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 simple two-parameter read tool with no output schema and no annotations, the description covers the chain, return fields, and cost. It could be more complete by clarifying parameter types and alternatives, but the essential calling context is present.

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%, so the baseline is 3. The description adds that the balance is for an ERC20 token and an address, and that symbol/decimals are resolved, but it does not clarify that the `token` parameter is a contract address rather than a symbol.

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 a specific resource and chain: ERC20 token balance on Base. It is clear what the tool returns, but it does not explicitly distinguish itself from sibling tools such as evm_balance or evm_portfolio.

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 only usage guidance is the tautological 'Use it to read a token balance.' It does not say when to choose this over evm_balance, evm_portfolio, or evm_token_info, nor does it state exclusions or prerequisites.

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