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

Annotations already declare readOnlyHint, destructiveHint=false and idempotentHint=false, and the description usefully reinforces idempotence by noting each call is charged so repeats are not free. It also discloses error behavior (malformed address returns 400, uncharged) and pricing, which the annotations do not cover. It stops short of describing the response shape, but that is a minor gap.

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 core purpose and the recommended usage come first, and every clause about proxies, pricing, and error handling carries real information. It is dense and packs commercial/error details into the middle, which slightly dilutes the front-loading but avoids waste.

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 still explains the return content (bytecode size, proxy status, implementation target), plus pricing, error handling, and the alternative tool. For a simple one-parameter read tool, nothing an agent needs 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?

Schema coverage is 100% on a single address parameter, so the baseline is 3. The description adds meaning by giving a concrete example value and the malformed-input behavior (400, uncharged), which helps the agent format and validate input.

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 Mantle is a smart contract or a plain wallet') and enumerates the payload the answer carries (bytecode size, EIP-1167 minimal proxy status, implementation address). This goes well beyond restating the name and differentiates it from the sibling mantle_proxy and *_balance 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 trigger ('Use before sending funds or approving a spender') and names an alternative for a different need ('for a fuller risk verdict use check_counterparty'). An agent knows exactly when this tool is the right pick.

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