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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered by structured data. The description adds genuinely new behavioral facts beyond that: the tool is pay-per-call at $0.01 USDC via x402, meaning a payment/auth flow is required, and supported networks include base-sepolia, which the prose omits. It does not mention rate limits or whether failed lookups are still billed.

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?

The core payload is front-loaded in a single dense but purposeful sentence, followed by a short usage clause and the price tag; nothing is redundant. The middle sentence is very long, packing a dozen sub-items, which slightly hurts scannability but every item earns its place.

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 carries the burden of describing return values, and it does so thoroughly by enumerating the fields and noting the risk verdict comes 'with reasons'. Remaining gaps are minor: response shape/ordering and error behavior (e.g. unknown address) are unstated, and base-sepolia is missing from the prose network list.

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%, and the schema already spells out the address pattern and the chain enum with its default. The description restates the network list (minus base-sepolia) but adds no syntax, format, or checksum guidance beyond what the schema provides, 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 names a precise resource (an EVM address) and enumerates exactly what is returned (EOA/contract/EIP-7702 classification, age, tx count, balances, Sourcify source, proxy info, labels, risk verdict), which is far beyond a restatement of the name. It does not explicitly contrast itself with siblings such as counterparty_risk_evm or screen_transaction, both of which also produce risk-flavored output, so the boundary is left implicit.

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?

"Useful to know who an address is before paying, listing or trusting it" gives concrete decision contexts for calling it. There is no explicit when-not guidance and no named alternative (e.g. when to prefer counterparty_risk_evm for a pure risk check), so it falls short of the full when/when-not/alternatives bar.

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