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

With no annotations, the description carries the full burden and does substantial work: it enumerates the verdict categories, lists the screening sources (OFAC SDN, Circle/Tether freezes, exploit/phishing/mixer labels, Bazaar track record), and — unusually valuable — discloses that the tool is itself paid at $0.003 USDC per call on Base. It does not cover failure modes (unreachable endpoint, malformed 402, timeouts) or latency, which is why it stops short of a 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?

Two sentences, front-loaded with the decision question and followed by a terse enumeration of checks and the return value; the pricing line is placed last where it belongs. The middle clause-stack is dense but every item is substantive, with no filler or repetition.

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 4-parameter, no-annotation, no-output-schema tool, the description gives the agent enough to decide to call it: what verdicts come back, what signals feed them, and what the call costs. The remaining gap is edge-case behavior (unreachable endpoint, malformed payment terms already counted as 'broken payment terms' but not defined), which keeps it below 5.

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%, so the schema already documents url, maxUsd, method and expectPayTo, including 'higher price -> block' and 'any other -> block'. The description adds only marginal meaning beyond that, notably the notion of 'decoy prices' being checked against maxUsd and the pairing of expectPayTo with the expected-payTo check. That is a light value-add over an already complete schema, so baseline 3 fits.

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?

Opens with a concrete framing question ('Should I pay this x402 endpoint?') and states the specific output: a pay/caution/block/cannot_pay verdict plus the payment option a standard client would sign. That is unambiguous verb+resource. It never names the adjacent siblings (x402check_check, x402check_origin, safepay_pass), so differentiation is by subject matter alone rather than by explicit contrast.

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 framing question implies use before paying an x402 endpoint, and the price disclosure hints it is a metered step rather than a bulk tool. However, there is no explicit 'use this when / not when', no mention of when to prefer x402check_check or sanctions_screen alone, and no prerequisites (e.g. whether the endpoint must be reachable).

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