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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=true and idempotentHint=false. The description goes further on the points annotations can't carry: $0.01/call pricing, 25 free calls, failed calls free, and a 400 on malformed addresses being uncharged. However, it never states whether results are paginated, truncated at 50 with a cursor, or what happens when a wallet has more than 50 transfers in the window.

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?

Scope and the sibling alternative are front-loaded, and the example is useful. The final sentence packs pricing, free tier and charging caveats into a dense run-on, which is informative but less scannable than the opening.

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?

With no output schema, the description still tells the agent what comes back (direction, counterparty, amount, transaction, newest first, up to 50). Combined with error behavior (400 uncharged), pricing and read-only nature, an agent has enough to call this 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 schema already documents token, blocks and address, including the 1-2000 range and default 1000. The description adds the practical framing (default USDC, "over the last N blocks") and a concrete address example, but no new syntax or format semantics. Baseline 3 is correct when the schema does the heavy lifting.

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 ("List a wallet's recent transfers of one ERC-20 token") plus chain, direction ("in and out"), window, and returned fields. It explicitly distinguishes itself from base_token_balance, so an agent can separate the two 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 the use cases ("confirm a payment arrived or see what was sent") and names the alternative tool for the other need ("for the current balance use base_token_balance"). The default token and block window are stated up front, leaving nothing to infer.

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