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

With no annotations, the description carries the full burden, and it does well: it discloses the 20-item cap, the return shape (per-item result plus overall verdict and safe_to_pay flag), the exact price ($0.01 USDC on Base eip155:8453), and how payment is passed via params._meta["x402/payment"]. That is substantial context an agent could not get from structured fields. It omits error/partial-failure behavior and rate limits, so it falls short of 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?

Dense and front-loaded: purpose first, then return shape, then pricing/payment mechanics, then transport. Every sentence adds information. The pricing clause sitting mid-paragraph slightly interrupts the purpose-to-usage flow, but there is 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 paid batch tool with no output schema, the description usefully explains what comes back and what payment is required. It is incomplete on the input side: the actual serialization of the batch payload is unstated and the advertised tx-hash mode has no visible parameter, leaving an agent unsure how to construct the call.

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 0% and the single parameter (urls) is undocumented in both schema and annotations, so the description must compensate and largely does not. It says "up to 20 URLs" but never explains how 20 values fit into a single string-typed field (array, delimiter, JSON) nor where the claimed settlement tx hashes are supplied, which conflicts with the schema's lone urls property. This format ambiguity is a real invocation risk.

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?

Specific verb plus resource: "Vet up to 20 x402 seller URLs in one call, or verify up to 20 settlement tx hashes." It also signals batching via "in one call", which implicitly contrasts with single-item siblings. It never names a sibling (x402_preflight__check, __verify, __screen) to route the agent explicitly, so it does not reach 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?

The batch mode and the dual-method capability (URLs vs settlement tx hashes) are stated, which implies when to use this tool rather than a single-item check. However, there is no explicit "use __check for one item, __batch for many" steer and no statement about limits like partial failure or when a batch is inappropriate, so the guidance remains implied rather than explicit.

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