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

Annotations cover the read-only/non-destructive profile, and the description adds meaningful context beyond them: malformed address or slot is rejected with 400 and uncharged, failed calls are free, and each successful call is charged so repeats are not free — which directly explains the idempotentHint=false annotation. Pricing and auth (x402 USDC, card key /credits, 25 free) are also disclosed.

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 purpose, slot semantics, and routing before the pricing tail, and every element is useful. Minor redundancy in stating the billing model twice ('Price $0.01/call…' and 'each call is charged, so repeats are not free') keeps it just short of ideal.

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 compensates by describing the returned value, and it covers error behavior, billing, and the proxy alternative. An agent has everything needed to call it correctly and interpret the result.

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%, so baseline is 3. The description goes further by explaining what a slot means (decimal index or 0x 32-byte key, used for mapping and proxy slots) and gives a concrete example address, which adds semantic value beyond the schema's type declarations.

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 Unichain') and even names the underlying RPC method (eth_getStorageAt). It also describes the return shape (32-byte word as number, address when applicable), letting an agent distinguish it from unichain_call and unichain_proxy without opening any 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 ('inspect contract state that has no getter, owners or implementation pointers') and an explicit alternative and exclusion ('for proxies use unichain_proxy'). Nothing about routing is left to inference.

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