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

With no annotations, the description carries the full burden and does meaningful work: it discloses that the tool is paywalled at $0.004 per call, names the accepted payment assets and chains, and explains the two-step sign-then-pay handshake. It does not cover failure behaviour, whether the first call's terms expire, or whether a retry re-charges, which keeps it below 5.

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 sentences, front-loaded with what the data is, then price and mechanism. Nothing is padding, though 'really costs' and 'measured from arrivals' lean slightly rhetorical rather than informative.

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 one-parameter paid lookup with no output schema, the description covers both the return content (arrivals with credited amount and fee, fees by size) and the payment protocol needed to invoke it. A brief note on what a returned purchase or a failed payment looks like would close the remaining 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 single parameter is fully documented in the schema, so baseline would be 3. The description earns the extra point by giving `payment` operational meaning the schema does not: the first call is made without it to retrieve terms, and it is only supplied after external wallet signing.

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 names a specific quantity and source: observed fees for USDC arrivals into Arc via Circle CCTP, broken into per-arrival credited amounts and fees plus fees grouped by size. That is far more specific than the tautological title. It stops short of naming a sibling (e.g. arc_bridges or arc_x402_stats) to contrast with, so a 4 rather than a 5.

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 a concrete operational sequence: call once without `payment` to obtain terms, sign with your own wallet, call again with `payment`. That is clear invocation context. What is missing is when to choose this over adjacent tools like arc_bridges or arc_fee_flow, so no exclusions or alternatives are stated.

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