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

Goes well beyond the annotations: explains that a malformed address is rejected with 400 and uncharged, states pricing ($0.01/call via x402 USDC or card key, first 25 free, failed calls free), and reconciles the idempotentHint=false with the read-only nature ('each call is charged, so repeats are not free'). That billing-driven non-idempotency is exactly the kind of trait annotations cannot convey.

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?

One dense, front-loaded paragraph: purpose first, then usage, then failure mode, then pricing. Every sentence carries information, though the pricing and billing detail is slightly heavy relative to the one-line core operation.

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 correctly compensates by naming the return content (bytecode size, proxy flag, implementation address). The only gap is that it does not clarify how its proxy detection relates to the dedicated celo_proxy tool, leaving a small ambiguity for an agent choosing between them.

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, so the baseline is 3, but the description adds a valid example address and the validation behavior for malformed input, which meaningfully informs how to prepare the argument.

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?

A specific verb plus resource ('Check whether a 0x address on Celo is a smart contract or a plain wallet') with the returned signal spelled out: bytecode size, EIP-1167 minimal proxy status, and the implementation it points to. The Celo prefix in the name and the explicit scope make it distinguishable from the dozens of other chain-level is_contract siblings.

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 pre-condition ('Use before sending funds or approving a spender') and names the escalation path ('for a fuller risk verdict use check_counterparty'). What it doesn't address is the relationship to the sibling celo_proxy, which appears to overlap with the EIP-1167 proxy detection this tool also returns.

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