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

With no annotations supplied, the description carries the full behavioral burden and discloses the paid x402 cost, required wallet signing, the two-call sequence, and that results come from real receipts rather than docs. It does not cover rate limits, data freshness, or error behavior, which keeps it from a top score.

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 tight sentences: purpose and measurement first, price second, invocation flow third. Every sentence adds useful information without repetition or 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?

Given the absence of an output schema, the description explains what the output represents: percentiles per transaction kind with sample sizes. The payment flow and pricing are fully covered, though it could say more about the result structure or supported transaction kinds.

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 single payment parameter is fully described in the schema as a signed x402 payment payload. The description adds meaningful process semantics around that parameter: the first call without payment returns terms, and the second call with payment completes the purchase.

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 states a specific resource and measurement: real transaction costs on Arc, reported as percentiles per transaction kind with sample sizes. It distinguishes the data from documentation quotes, but does not explicitly differentiate itself from sibling cost/price tools such as arc_cctp_cost or arc_fee_flow.

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?

It gives clear invocation guidance for the paid flow: call once without payment to get terms, sign with your own wallet, then call again with payment. It does not explicitly state when to use this versus alternative cost-related tools, but the context is clear enough for an agent to act.

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