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

Goes well beyond the annotations: malformed addresses are rejected with 400 and uncharged, failed calls are free, each successful call is billed at $0.01 via x402 USDC or a card key, and the first 25 are free. It also explains the otherwise puzzling idempotentHint=false by noting repeats are charged, and restates the read-only nature ('reads or computes only and changes nothing'). It stops short of describing latency or rate limits.

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-loaded with purpose and usage, then return fields, then error behavior, then pricing. Nearly every clause is informative, though the pricing/billing sentence is long and packs three separate facts that could be split for scanability.

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 compensates by naming the returned facts (bytecode size, minimal-proxy flag, implementation address). Combined with error behavior, pricing, and the alternative tool, an agent has everything needed to call it correctly and interpret the result.

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 there is only one parameter, so the schema already carries the load. The description still adds validation semantics (malformed address → 400, uncharged) and a concrete example address, which is more than the bare '0x address' schema text.

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 Gnosis is a smart contract or a plain wallet') and enumerates exactly what is returned: bytecode size, EIP-1167 minimal-proxy status, and implementation address. The chain prefix in the name plus this enumeration separates it from the many sibling chain variants, though it never explicitly contrasts itself with gnosis_proxy despite mentioning proxy detection.

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 a concrete decision context ('Use before sending funds or approving a spender') and names the alternative for the heavier case ('for a fuller risk verdict use check_counterparty'). The agent knows both when to call this and when to route elsewhere.

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