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

Annotations already declare readOnlyHint/destructiveHint/idempotentHint/openWorldHint, but the description adds real context beyond them: malformed addresses rejected with 400 and uncharged, pricing ($0.003/call, first 25 free, failed calls free), and 'each call is charged, so repeats are not free' which reinforces the non-idempotent/costly nature. This is a rich disclosure of failure and billing behavior.

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 purpose, scope, and usage before pricing details; every clause carries information. It is dense and pricing-heavy, but nothing is redundant filler, so it stays readable.

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 fully describes the return shape (direction, counterparty, amount, transaction, newest-first, up to 50). Combined with the error and billing behavior, an agent has everything needed to call it correctly.

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, but the description adds the USDC default, the 1-2,000 block range with default 1,000, and a result cap ('up to 50') that is not represented in any parameter. It goes modestly 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?

Specific verb+resource ('List a wallet's recent transfers of one ERC-20 token ... in and out, over the last N blocks') with explicit scope and output fields. It names the sibling it is not ('for the current balance use eth_token_balance'), so an agent can distinguish it from eth_token_balance 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?

States the use case ('confirm a payment arrived or see what was sent') and names the alternative tool with the condition that selects it (eth_token_balance for current balance). The when-to-use and when-not-to-use are both explicit.

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