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

Goes well beyond the annotations: discloses error behavior (malformed address or slot rejected with 400, uncharged), billing model ($0.01/call, first 25 free, failed calls free), and that repeats are charged — which explains why idempotentHint is false for what is otherwise a pure read. It also confirms no state change occurs.

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 return shape, then usage and pricing. Slightly redundant at the tail where 'each call is charged, so repeats are not free' restates the price sentence, and 'reads or computes only and changes nothing' partly duplicates the readOnly annotation.

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 only two parameters, no output schema, and safety already covered by annotations, the description supplies everything needed: return format, slot key forms, error semantics, and cost. Nothing required for correct invocation is missing.

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 schema already documents both address and slot (decimal index or 0x 32-byte key). The description adds only the mapping/proxy rationale for key-form slots and an example address; notably it never states what slot defaults to when omitted.

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 (read one raw storage slot of a contract on Ethereum), names the underlying RPC method eth_getStorageAt, and describes the return shape (32-byte word as number, and as an address when applicable). This clearly separates it from generic call/balance siblings and from eth_proxy.

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 explicit usage context ('contract state that has no getter, owners or implementation pointers') and names the alternative for the proxy case ('for proxies use eth_proxy'). Slight internal tension remains because implementation-pointer slots are themselves proxy-related, but the intended routing is still clear.

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