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

Adds substantial context beyond the annotations: pricing ($0.01/call via x402 or a card key, first 25 free, failed calls free), that failures are uncharged, and that reads change nothing. The 'each call is charged, so repeats are not free' line usefully explains why idempotentHint is false. Missing only whether the balances are read at latest block or a pinned block.

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?

One front-loaded paragraph that puts the purpose and return shape first, then the alternative, then error/pricing details. Dense and mostly waste-free, though the pricing/club-of-details at the end is packed tightly enough to be easier to skim if split.

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, and the description compensates by naming the returned fields (raw amount, decimals, symbol, human-readable amount) and describing error behavior and cost. The only real hole is the ambiguity about whether the token argument takes a ticker, which it elsewhere implies it does.

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 does add the 0x/40-hex format constraint, but 'Both inputs are 0x addresses' conflicts with the schema's allowance of a ticker ('USDC, USDT, WETH') for the token parameter, which leaves the accepted format ambiguous rather than clarified.

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 ('ERC-20 token balance of a wallet on Sei'), names the contract method (balanceOf), and enumerates the returned fields. It also explicitly separates itself from the native-coin sibling sei_balance, so an agent can route without opening a schema.

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 an explicit use case ('check stablecoin or token holdings before a transfer or trade') and an explicit alternative ('for the native coin use sei_balance'). It also names the failure conditions (404 for no contract, 422 for a non-ERC-20 contract) so the agent knows when the call will not produce a value.

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