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

Goes well beyond the annotations: discloses pricing ($0.01/call, 25 free, failed calls free), rejection behavior (400, uncharged), and explicitly explains why repeated calls are not free — which is the reason the annotations mark idempotentHint=false. It only lightly repeats readOnlyHint with 'changes nothing', so the added context is real. It could be stronger on whether the returned word is always present or null for an empty slot.

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 return shape, then the routing rule, then pricing. Dense but every element (pricing, 400 behavior, example, sibling pointer) earns its place. Slightly overpacked into a single block, which costs it a point.

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?

No output schema exists, yet the description explains what comes back (32-byte word as a number, and as an address when it holds one). With annotations covering safety and the description covering return shape, routing, failure mode, and cost, an agent has everything needed to call it correctly.

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 already documents both parameters, so the description only needs to add value — it does by explaining that slots are decimal indices or 0x 32-byte keys used for mapping and proxy slots, and by giving a concrete address example. This exceeds the baseline-3 case where schema carries all meaning.

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 Avalanche), maps it to the underlying RPC (eth_getStorageAt), and describes the return shape. It also names the sibling it is not (avax_proxy), so an agent can distinguish it without opening either 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?

Explicit when-to-use ('contract state that has no getter, owners or implementation pointers') with an explicit alternative and routing rule ('for proxies use avax_proxy'). The when-not case and failure condition (malformed address/slot -> 400, uncharged) are both stated.

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