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

Goes well beyond the annotations: discloses that malformed addresses return 400 uncharged, that failed calls are free, the $0.003/call x402 pricing and 25 free calls, and result behavior (newest first, capped at 50). It also proactively reconciles the non-obvious readOnlyHint=false, which would otherwise look like a mutation signal.

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?

A single dense paragraph with the core action front-loaded before usage, errors and pricing. Every clause carries information, though the pricing/annotation-rationale tail makes it longer than strictly necessary for invocation.

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 supplies the return shape (direction, counterparty, amount, transaction, ordering, cap) plus cost and error semantics. Nothing needed 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 description coverage is 100%, so token, blocks and address are already documented, and the description largely restates the defaults. It does add one fact absent from the schema (the 50-result cap), but otherwise 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 (List) plus resource and scope: a wallet's ERC-20 transfers on Arbitrum One, in and out, with default token, block window and result ordering. It also names the network implicitly and distinguishes itself from the balance sibling, so an agent can place it without opening the 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?

Explicit when-to-use ('confirm a payment arrived or see what was sent') and an explicit alternative for the adjacent need ('for the current balance use arb_token_balance'). No inference required to pick between the two.

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