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

With no annotations, the description carries the full burden and does well: it discloses the cost and payment rail ('Paid $0.001 (x402, USDC Base)'), the read mechanism (public Base RPC eth_call balanceOf), and the return shape (raw + human balance, decimals, symbol). It stops short of failure modes, rate limits, or behavior for non-ERC20 contracts.

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?

A single dense sentence: cost and payment rail first, then the operation, mechanism, and return values. Zero filler and nothing redundant.

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 two-parameter tool with no output schema, the description covers what is returned, how it is fetched, and that it costs money. Nothing essential for invoking it correctly is missing, though edge-case behavior (invalid token, non-ERC20 contract) is unaddressed.

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 both parameters are already documented, and the description adds only indirect meaning ('any Base address' for the wallet, balanceOf implying the contract is an ERC20 token). No format, checksum, or validation details are added 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?

States a precise verb+resource: 'on-chain ERC20 token balance for any Base address'. It also names the mechanism (eth_call balanceOf) and the chain (Base), which distinguishes it from price-oriented siblings such as get_crypto_price or get_usd_price.

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 description implicitly scopes usage by naming Base as the network and ERC20/token contract as the resource, so an agent can infer it must not be used for other chains or native-asset balances. However it never states when to prefer this over price or verdict siblings, and gives no exclusions or prerequisites beyond the implicit ones.

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