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

Annotations are non-obvious (readOnlyHint=false on what is a pure read), and the description directly reconciles this: 'Reads or computes only; not marked read-only because each call is charged.' It also discloses pricing ($0.003/call via x402 USDC or card key), free tiers, and that failed calls are free — context no annotation field carries.

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 the core purpose, then use case, alternative, error handling, and pricing — each sentence carries information an agent needs for routing or invocation. It is dense with billing detail but nothing is wasted; slightly heavier than strictly necessary.

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?

There is no output schema, and the description compensates by naming the returned fields (bytecode size, proxy status, implementation). Combined with error behavior and cost model, an agent has everything needed to decide whether to call and to 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?

Only one parameter and schema description coverage is 100%, so the schema already documents 'address'. The description adds a concrete example address, which helps with format, but does not add chains/validation/normalization semantics beyond that. Baseline 3 is appropriate.

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 Base address is a contract vs wallet) and enumerates the returned facts: bytecode size, EIP-1167 minimal-proxy status, and the implementation address. This clearly separates it from the many sibling is_contract tools on other chains and from check_counterparty.

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 the escalation path ('for a fuller risk verdict use check_counterparty'). It even specifies malformed-input behavior (400, uncharged), so the agent knows the failure mode before calling.

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