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

Goes well past the annotations (readOnlyHint, openWorldHint, idempotentHint=false, destructiveHint=false) by disclosing pricing ($0.01/call via x402 USDC or card key), the 25-free-call allowance, that failed calls are free, that malformed addresses return 400 uncharged, and that repeats are charged — the latter actively reinforcing idempotentHint=false. Also restates the no-side-effect guarantee in plain language.

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?

Front-loads the core operation and outputs, then usage, then error/pricing terms — each sentence carries distinct information. The closing 'reads or computes only and changes nothing' partially repeats the safety point implied earlier, but it is short and the pricing detail (repeats cost money) is non-obvious and 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?

No output schema exists, yet the description enumerates the return values (bytecode size, proxy status, implementation) so the agent knows what it gets. With annotations covering safety, the addition of pricing, error handling, and an example makes this complete for a one-parameter read tool.

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 description adds real value beyond it: a concrete example address, the '0x address' format expectation, and the failure behavior (400, uncharged) for malformed input. It does not specify accepted casing or checksum requirements, which keeps it from a 5.

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 (check whether a 0x address on Polygon PoS is a contract or wallet) and lists exactly what comes back: bytecode size, EIP-1167 minimal-proxy status, and implementation address. The polygon_ prefix plus the explicit sibling reference (check_counterparty) makes it distinguishable from the ~100 other tools.

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?

Gives an explicit use case ('before sending funds or approving a spender') and names the alternative with the condition that selects it ('for a fuller risk verdict use check_counterparty'). It also notes which sibling covers the combined proxy+contract question, so the agent need not infer routing.

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