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

Annotations already cover safety (readOnly, idempotent, non-destructive, openWorld), yet the description adds substantial non-obvious behavior: the response includes implementation and admin addresses, and there is a 10 calls/day free tier with x402 micropayment ($0.001/call, via params._meta["x402/payment"] or HTTP) or X-API-Key credits. Rate limits and payment mechanics are exactly the kind of operational detail an agent needs before calling. It stops short of describing behavior for non-proxy contracts (e.g. what is returned when no proxy pattern matches), which keeps it from a 5.

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 question and detection list, with pricing folded into a separate clause at the end. Every clause carries information, though the payment sentence is dense and packs three mechanics into one line.

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?

For a two-parameter read tool with an output schema, the description covers purpose, detection scope, return highlights, cost, and authentication options. Only the edge-case behavior (non-proxy or unrecognized contracts) is left unstated, which is a minor gap given the output schema.

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 description coverage is 100% and the schema itself documents both parameters, including an enumerated set of chain values in the chain description. The tool description adds no additional meaning about chain or address formatting, so the baseline 3 applies.

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?

Opens with a specific question the tool answers ('Is this contract upgradeable?') and then enumerates exactly what it detects: EIP-1967 impl/admin/beacon, EIP-1167 clones, legacy OZ and Safe-style proxies, EIP-7702 delegated EOAs. That level of specificity clearly separates it from siblings like address_profile or contract_read, which do not describe proxy-pattern 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?

The framing question implies the use case (checking upgradeability of a given contract), but there is no explicit when-to-use/when-not-to-use guidance and no sibling is named as an alternative. An agent can infer the scenario, but must decide routing on its own.

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