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

Annotations cover the safety profile, but the description adds non-obvious context: the call costs $0.001 USDC on Base via x402, which explains both the payment/auth requirement and why readOnlyHint is false despite this being a query. It also discloses that the returned nonce includes pending transactions, useful for correctness. Return format beyond that is unspecified, keeping it at 4.

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: the core value is front-loaded, the use cases follow, and the cost caveat comes last. Every sentence earns its place with no filler.

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-parameter query with no output schema, the description adequately conveys what is returned (the nonce, confirmed + pending) and the payment precondition. Only minor gaps remain, such as the exact return shape or error behavior on a non-existent address.

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?

Single parameter with 100% schema description coverage, so the schema already documents the address field. The description adds no syntax or format detail for the address (e.g., chain-specific handling or validation), so the baseline 3 applies.

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+resource: the transaction count (nonce) of an address, scoped to Optimism, and clarifies the value is both confirmed and pending. This distinguishes it cleanly from siblings like op_tx, op_balance, op_receipt and from the same-named nonce tools on other chains (eth_nonce, arb_nonce, polygon_nonce).

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 two concrete use cases (to build the next transaction, or to tell whether an address has ever sent anything), which tells the agent when this tool is the right pick. It stops short of naming alternatives or stating exclusions (e.g., using a different chain's nonce tool), so it lands at clear context without explicit routing.

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