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

Adds substantial context beyond the annotations: the 400/404 failure semantics, that failures are uncharged, pricing ($0.01/call, first 25 free), and that repeat calls are billed — which directly explains the non-obvious idempotentHint=false. The 'reads or computes only and changes nothing' line corroborates readOnlyHint/destructiveHint rather than contradicting them.

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 action and the slot standards, then usage, errors, example, and pricing in a sensible order. The billing point is stated twice ('failed calls free' then 'each call is charged, so repeats are not free'), a minor redundancy in an otherwise dense block.

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 does the work of describing the return ('names the kind found') and lists the kinds it can detect, which is the key output shape. It omits the non-error, non-proxy case (what is returned when no proxy pattern is found), leaving one meaningful gap for a resolution 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% and the single parameter is already documented as '0x contract address', so the schema carries most of the load. The description still adds value with a concrete checksummed example and by tying malformed-address input to a specific 400 outcome.

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 ('Find the implementation behind a proxy contract on Ethereum') and enumerates exactly which storage slots and bytecode patterns it inspects, so the agent knows the resolution depth. The 'on Ethereum' scope plus the named sibling contract_risk distinguish it from the arb_/base_/op_/polygon_proxy family.

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 clear trigger ('Use before trusting or decoding a contract whose code can be swapped by its admin') and routes to an alternative for a different need ('for a fuller risk verdict use contract_risk'). No explicit when-not-to-use statement, which keeps it just below the top mark.

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