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

Annotations supply the safety profile (readOnlyHint false, openWorldHint true, idempotentHint false, destructiveHint false), but the description adds materially: the call costs $0.001 in USDC on Base via x402. That payment/auth requirement is behavioral context the annotations don't carry. Return-shape and failure behavior are not described.

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?

Three tight sentences, front-loaded with the resource, then the field list, then usage and cost. The field enumeration is slightly list-heavy but earns its place given there's no output schema.

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 single-param, no-output-schema tool, the description is nearly sufficient: it lists the returned fields and discloses the payment model. It doesn't cover edge cases like invalid block numbers or error/refund behavior, which would round it out.

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 there is only one parameter, so the schema already documents 'number'/'latest' (default). The description restates 'by number, or the latest one' without adding format detail, so baseline 3 is appropriate.

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 resource (an Optimism block, by number or latest) and enumerates the returned fields (hash, timestamp, tx count, gas used/limit, base fee in gwei, producer). The chain name cleanly distinguishes it from the many sibling *_block tools (arb_block, eth_block, base_block, etc.).

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?

'Use for timestamps, confirmations and chain-activity checks' gives clear intended use cases. It stops short of naming when NOT to use it or pointing to an alternative (e.g. op_gas/op_tx), so it's context without exclusions.

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