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

Goes well beyond the readOnly/destructive/openWorld annotations: it discloses that malformed addresses are rejected with 400 and uncharged, that pricing is $0.01/call with 25 free and failed calls free, and that repeated calls are billed again. That last point usefully explains why idempotentHint is false, and the 'reads or computes only and changes nothing' clause reinforces the safety profile rather than contradicting it.

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 purpose and the returned fields are front-loaded, and the alternative routing and pricing follow in a logical order. The pricing/billing sentence is dense and slightly long, but each clause carries operational information an agent needs before spending money.

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, yet the description enumerates the response contents (bytecode size, proxy status, implementation address), so an agent knows what it will receive. Combined with error handling, cost, and safety notes, nothing material is missing 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 a single required 'address' parameter, so the baseline would be 3. The description earns an extra point by supplying a concrete example address and by stating the validation behavior (malformed address yields 400), which the schema's bare '0x address' field does not convey.

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 Ethereum is a smart contract or a plain wallet — and enumerates exactly what is returned (bytecode size, EIP-1167 minimal-proxy status, implementation target). The 'on Ethereum' scoping plus the explicit contrast with check_counterparty lets an agent distinguish it from the many sibling *_is_contract tools without opening a schema.

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 adjacent need ('for a fuller risk verdict use check_counterparty'). That is explicit when-to-use plus explicit alternative routing, which is the top of this dimension.

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