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

Annotations declare readOnlyHint=false, idempotentHint=false, destructiveHint=false. The description adds critical cost information ($0.001 USDC on Base per successful call, paid via x402), which is not in annotations. It does not explain error handling or the exact return format, but the cost disclosure is a significant behavioral addition.

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 dense sentences: first states the core function and extra data, second provides critical usage and pricing context. No wasted words; front-loaded with purpose.

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?

For a simple read-only check with one parameter and no output schema, the description covers purpose, usage, and cost. It does not mention what happens on failure or exact return structure, but overall sufficient for an agent to call correctly.

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 single parameter 'address' is fully documented. The description does not add syntax or format details beyond what the schema provides, so 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+resource: determines whether an address on Polygon PoS is a smart contract or plain wallet, and discloses bytecode size and EIP-1167 minimal proxy status. Clearly distinct from siblings like polygon_balance or eth_is_contract (different chain).

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?

Provides a clear usage context: 'Use before sending funds or approving a spender.' Does not explicitly name alternatives or exclusions, but the purpose is narrow enough that an agent knows when to invoke it.

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