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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true, so safety is covered. The description goes further in useful ways: it discloses pricing ($0.01/call, first 25 free, failed calls free), the 400 rejection of malformed addresses without charge, and the non-idempotent billing behavior that explains idempotentHint=false. That is real added context beyond structured fields, though return shape and block-lag semantics are not described.

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?

Purpose and scope are front-loaded in the first clause, then alternatives, then failure/pricing behavior. It is dense and every sentence carries information, but the pricing and example sentences make it slightly longer than strictly needed for tool selection.

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 single-parameter read tool with no output schema, the definition covers what it returns (wei and SEI), at what block, what inputs are valid, what happens on bad input, what it costs, and what it does not cover (tokens, portfolios). Nothing an agent needs in order to call 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%, so the single parameter is already documented; the description still adds value with an explicit 'any 0x wallet address' constraint, a concrete example address, and the fact that malformed input yields a 400 rather than a partial result. That is meaningful validation semantics beyond the schema's one-line property description.

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+resource: the native SEI balance (eth_getBalance) of any 0x address on Sei at the latest block, returned in both wei and SEI. It explicitly separates itself from sei_token_balance (ERC-20) and wallet_portfolio (all holdings), so an agent can distinguish it from the dozens of sibling *_balance tools 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 a concrete use case (check whether a wallet can pay gas or a transfer) and names two alternatives with the condition that selects each: sei_token_balance for ERC-20s, wallet_portfolio for all holdings at once. No inference required.

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