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

Annotations declare openWorldHint, non-readOnly, non-idempotent, and non-destructive. The description adds critical behavior beyond annotations: a $0.001 USDC cost per successful call via x402, and the return contents (bytecode size, EIP-1167 proxy status, implementation address). It omits auth/header details and error behavior, keeping it from a 5.

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?

Three sentences, front-loaded with the core purpose, then usage advice, then cost. Every sentence earns its place and no information is redundant.

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 return-value burden and does so by naming key return fields. It also covers chain, cost, and use case. It could be more explicit about the x402 payment flow or error cases, but it is otherwise complete for a paid single-address query.

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% for the single address parameter, and the schema already documents it as a 0x address. The description adds only 'address on Base', which does not meaningfully extend parameter semantics beyond the schema. 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?

States a specific chain (Base), the exact check (smart contract vs plain wallet), and extra outputs (bytecode size, EIP-1167 minimal proxy, implementation address). This distinguishes it from sibling is_contract tools on other chains and even from a generic contract check.

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 says when to use it: before sending funds or approving a spender. Clear context, but does not name alternatives or state when not to use it (e.g., use eth_is_contract for Ethereum addresses).

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