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

Annotations declare readOnlyHint=false, which is unusual for a read tool; the description proactively explains why ('not marked read-only because each call is charged'), resolving the apparent anomaly. It further discloses error behavior (malformed addresses rejected with 400, uncharged), pricing and payment paths, free-tier terms, and result ordering/caps — well beyond what the annotations provide.

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 is front-loaded in the first clause, followed by usage, error, and cost information in a compact flow. It is dense — purpose, parameters, error handling, and pricing are packed into three sentences — but nearly every clause carries decision-relevant information for an agent deciding whether to call.

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 covers the returned fields (direction, counterparty, amount, transaction), ordering (newest first), the cap (up to 50), error semantics, and pricing. Nothing material for correct invocation 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 description coverage is 100% and the schema already documents the token default, block range, and address format, so the description's re-statement of defaults is largely duplicative. The only genuinely new detail is the result cap ('up to 50'), which is output-centric rather than parameter semantics, so the baseline 3 applies.

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?

The description gives a specific verb and resource ('List a wallet's recent transfers of one ERC-20 token'), names the chain (Polygon PoS), the scope (in and out, last N blocks), and the default token (USDC). It explicitly distinguishes itself from the sibling polygon_token_balance, so an agent can route correctly without opening any 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?

It states the concrete use case ('confirm a payment arrived or see what was sent') and names the alternative tool plus the condition that selects it ('for the current balance use polygon_token_balance'). When-to-use and when-not-to-use are both covered.

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