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

No annotations are provided, so the description carries the full burden. It discloses the payment flow (two-step: terms then payment), the cost, and the fact that passing `payment` completes the purchase inside the tool call. It doesn't detail what happens after payment or whether the call is idempotent, but the two-step flow is clearly explained.

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 compact and information-dense. Every sentence earns its place: what the tool measures, the cost, the two-step usage pattern, and the parameter semantics. It front-loads the core purpose before explaining the payment flow.

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 tool with one optional parameter and no output schema, the description covers the essential context: purpose, cost, supported assets/networks, and the two-step payment flow. It doesn't describe the output format, but given the tool's simple interface and the absence of an output schema, this is a minor gap.

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?

The schema has 100% coverage for the single `payment` parameter, describing it as a signed x402 payment (base64 payload for PAYMENT-SIGNATURE). The description adds context about when to pass it (second call after signing terms) and that it completes the purchase, which goes beyond the schema's basic type description.

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 clearly states the tool's purpose: measuring the real cost of bringing USDC into Arc via Circle CCTP, with specific details about what is measured (arrivals, amount credited, fee taken, observed fees by size). It distinguishes itself from sibling tools like arc_bridges, arc_fee_flow, and arc_stablecoins by focusing on CCTP cost measurement from arrivals.

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 provides explicit usage guidance: call once without `payment` to get the terms, sign them with your own wallet, then call again with `payment`. It also states the cost ($0.004 per call over x402) and the supported networks (USDC on Arc, Base or Solana, or XNT on X1), which helps the agent decide when to use this tool.

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