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

Annotations only declare readOnly/idempotent/openWorld; the description adds the actual screening sources, the risk enum returned, example flags, the freshness disclaimer, and the full free-trial-then-paid-x402 flow including what not to do. The only deduction is the boilerplate payment prose restated in several forms, some of which repeats rather than adds.

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?

Essential purpose, trigger and alternative are front-loaded in the first three sentences. The tail, however, is a long payment-mechanics block plus two overlapping 'illustrative output excerpt / not a live result' disclaimers that pad rather than inform.

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?

An output schema exists, yet the description still explains the risk levels and flags usefully; combined with pricing, the at-least-one-input rule, and the sibling routing, an agent has everything needed to call it. Minor redundancy with the output schema rather than a 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?

Schema coverage is 100% (baseline 3), but the description adds a constraint the schema does not express: all three params are optional yet 'at least one of domain, address, or name' is required, and inputs may be combined. It also restates that domain accepts hostname or URL, which the schema already says.

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 verb and resource ('Screens a payee wallet address and name against the OFAC SDN sanctions list and checks the merchant domain's registration age and DNS') and names the sibling it is not (preflight_payment). An agent can distinguish it from check_token, check_endpoint and preflight_payment 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?

Explicit trigger condition ('Call this before a USDC payment when you only have a payee name, wallet or domain') plus an explicit alternative and the condition that selects it ('For an x402 challenge or cart... use preflight_payment instead'). Nothing is left to inference.

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