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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false), and the description reinforces it with "Reads or computes only and changes nothing." It adds genuinely useful non-annotation behavior: error semantics (unknown contract 404, non-ERC-20 422, both uncharged) and billing ($0.01/call, 25 free calls, failed calls free, repeats charged). That billing note also rationalizes the unusual idempotentHint=false, which is a real plus.

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?

Front-loaded with the resource and return shape, then usage, then constraints and pricing — a logical order with no filler sentences. It is dense, packing errors, pricing, and billing into one paragraph, but every clause carries information an agent needs.

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 enumerating the return fields. With error codes, pricing, the free tier, the input format, and the native-coin alternative all covered, an agent has everything needed to call it correctly and interpret a failure.

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 format guidance ("0x addresses, 40 hex characters"), but it overreaches by saying "Both inputs are 0x addresses" when the schema explicitly allows a ticker like USDC/USDT/WETH/DAI for the token parameter — a small inconsistency that could confuse an agent about accepted token input.

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 (ERC-20 balanceOf for a wallet on HyperEVM) and enumerates the exact return fields: raw amount, decimals, symbol, human-readable amount. It also explicitly separates itself from the native-coin sibling (hyperevm_balance), so an agent can pick the right tool 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 stablecoin or token holdings before a transfer or trade") and names the alternative with its selection condition ("for the native coin use hyperevm_balance"). Explicit when-to-use and when-to-use-something-else.

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