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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so safety is covered. The description adds valuable pricing information ($0.001 USDC per call) and enumerates supported chains, which are not in annotations. The API reference is redundant but harmless. With annotations covering the safety profile, this is above baseline.

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?

The description is three sentences, front-loaded with purpose and use case. The third sentence listing chains and an API reference is somewhat extraneous—chain list already appears in the schema—but it's not verbose. The description is efficient overall, though it could be trimmed without loss.

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 an output schema present, return values are defined elsewhere. The description covers purpose, cost, supported chains, and gives a concrete example of intended use. It doesn't discuss error handling or edge cases, but for a simple read operation with a comprehensive schema, this is adequate. A note about blockTag default is already in the 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%, so each parameter is already documented. The description adds a use-case hint (owner slot, mapping entry) that could help agents understand slot semantics, but it does not explain how to derive slot values or add meaning beyond the schema. Baseline 3 is appropriate when the schema carries the load.

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?

The description opens with 'eth_getStorageAt for one slot of one account', a specific verb and resource, and immediately clarifies its niche by contrasting with view functions ('instead of trusting a view function'). It clearly distinguishes from sibling tools like chain_storage_range (multiple slots) and chain_storage_diff, making the purpose unmistakable.

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 description implies when to use: when you need to verify raw storage rather than a view function. It does not explicitly name alternatives like chain_call or chain_storage_range, but the phrase 'instead of trusting a view function' gives context. It lacks an explicit 'when not to use' but the intent is reasonably clear.

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