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

Consistent with readOnlyHint=true/destructiveHint=false and reinforces it ('Reads or computes only and changes nothing'). Goes well beyond annotations: newest-first ordering, 50-result cap, 400 + uncharged on malformed addresses, failed calls free, and $0.01/call pricing with 25 free calls that makes repeat calls non-free.

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 what the tool returns and its scope, then usage routing, then error/pricing behavior. Dense but every sentence carries operational information (defaults, caps, error handling, cost) with no filler.

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, yet the description fully characterizes the return shape (direction, counterparty, amount, transaction, newest first, up to 50) and the failure mode. An agent has everything needed to call it correctly and to anticipate cost.

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 still reinforces the token default (USDC on this network), the 1-2,000 block range with default 1,000, and supplies a concrete example address. It does not add much on 'blocks' semantics beyond the schema, so it sits just above baseline.

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 ERC-20 transfers), the network (zkSync Era), direction (in and out), default token (USDC), window (last N blocks), and returned fields. An agent can distinguish it from zksync_token_balance or zksync_logs 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?

Explicitly gives the use cases ('confirm a payment arrived or see what was sent') and names the alternative for the adjacent question ('for the current balance use zksync_token_balance'). Also states the block-window default and the ~33-minute equivalency for the max, so the agent knows how to size the query.

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