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

With no annotations, the description carries the full burden and does so: deterministic, stateless, never pays anyone, one signed receipt returned, no charge when seller data is unavailable, and explicit pricing ($0.02 USDC on Base, paid in-band via x402 with _meta key). Side-effect profile (read-only, no funds moved) and pricing/failure terms are all disclosed.

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?

Front-loaded with the verdict summary, then trigger, then mechanics, then pricing/transport — a sensible order with little filler. The trailing HTTP endpoint URL and the dense parenthetical enumerations make it longer than strictly necessary, but each clause does convey something actionable.

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?

No output schema, yet the description explains the return payload (verdict + reasons + one signed receipt) and the charge/refund condition. Given no annotations and nested params, coverage is strong; the main gap is sellerRules override semantics, which an agent cannot infer from the schema enums alone.

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 only 40% across 5 params with nested objects, so the description does compensate for policy (limits, rolling cap, categories, allow/deny lists, hours, assets/chains, approval threshold) and the reputation dimensions. However, sellerRules (minScore, onCaution, onUnknown) and lookbackDays are never explained in prose, and `pass` (day-pass to skip payment) is only documented in the schema.

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?

States a specific decision verb and resource: it evaluates a payment against spend policy and seller reputation and returns one verdict (pay / dont_pay / ask_human). The bracketed lead and title make clear it composes the two sibling checks (check_spend_policy, check_seller_reputation) into a single answer, so an agent can distinguish it from those tools without opening a schema.

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?

'Use right before an agent pays an invoice, merchant or x402 seller' gives an explicit trigger point in the agent workflow. It does not explicitly say 'if you only need one check, call check_spend_policy or check_seller_reputation instead', so the sibling routing is implied rather than spelled out.

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