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

Despite readOnlyHint, openWorldHint, and idempotentHint annotations, the description adds substantial behavioral detail: paid via x402, the 402 challenge without payment, automatic payment via fiatdock-mcp, 400 for bad addresses, 502 when dependencies fail, and no charge for failed calls. This goes well beyond the annotations and does not contradict them.

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 description is dense but every sentence earns its place: pricing, enrichment contents, intended use case, payment flow, and error semantics. The paid aspect is front-loaded, and the information is organized in a scannable way.

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?

The output schema covers the return shape, and the description covers the operational context needed to invoke the tool correctly: cost, two-step payment, automatic payment path, error statuses, external dependencies, and triage use cases. Nothing critical 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?

The schema already documents both parameters at 100 percent coverage, so the baseline is 3. The description adds meaningful behavior around the payment parameter: OMIT it on the first call, the npm package pays automatically, and neither the 402 nor failed calls are charged.

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 clearly states the tool enriches a Base address in one call and enumerates the exact outputs: EOA vs contract, ERC-20 details, nonce, ETH/USDC balance, and a GoPlus security verdict. This distinguishes it from narrowly scoped siblings like eth_balance and usdc_balance.

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?

The description gives strong use context: use it before trusting a counterparty, payout target, or approval spender, and frames it as the loop input for triaging addresses. It does not explicitly name alternatives or state when not to use it, so it falls just short of a 5.

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