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

Annotations already declare readOnlyHint and openWorldHint, and the description adds genuinely useful context beyond them: the $0.003 USDC charge via x402 (a real auth/paid-call requirement) and an explicit 'Not an audit' scope limitation. It stops short of saying what happens on an unverified or non-contract address, which would complete the behavioral picture.

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?

Two tight sentences: the check contents come first, then the audit disclaimer and payment cost. No filler and nothing buried.

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 usefully enumerates the returned fields (is-contract, code size, owner, proxy implementation, verification status, notes), which covers most of what an agent needs. Missing only failure-mode behavior (non-contract addresses, unverified sources) and any indication of response shape.

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% for the single 'address' parameter ('0x-prefixed Base address'), so the schema carries the semantics. The description adds no format, validation, or edge-case guidance about the address itself, 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?

States a specific verb and resource ('Contract check on Base') and enumerates exactly what the check covers: contract existence, code size, owner(), proxy implementation, Sourcify verification of source and implementation, plus notes. This scope is clearly distinct from siblings like base_address or base_token, so an agent can route 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?

The 'Not an audit' disclaimer gives a partial when-not signal, and the cost line sets a payment precondition. However, it never states when to prefer this over sibling tools (e.g., base_address for a plain address lookup) or when the paid call is worth it, leaving selection to inference.

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