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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds context annotations cannot: the data is static, it carries a $0.10 USDC per-call x402 charge, and the first unpaid call returns payment requirements to be retried with an X-PAYMENT/PAYMENT-SIGNATURE header or params._meta["x402/payment"]. That is the single most important behavioral fact for an agent here — a naive call silently fails with a 402-shaped payload instead of a checklist. It stops short of stating whether payment is settled per call or can be reused across calls.

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 purpose and disclaimers before the payment mechanics, with no filler. The final sentence is dense — it packs three payment mechanisms into one clause — but every element is actionable and removing any would cost the agent real information.

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 two-parameter read-only lookup with no output schema, the description covers purpose, limits, and access mechanics well enough to invoke it correctly. The one gap is return shape: 'checklist' is not defined (list of obligations? citations? per-market grouping?), and with no output schema the description is the only place that could have said so.

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 description coverage is 0%, and the 7-value productType enum and 3-value markets array carry no per-value explanation in either schema or description. The description compensates only by naming the two axes ('by product type and market'), without explaining what happens when the optional markets array is omitted (all markets vs. none) or what the enum members imply for coverage depth.

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 concrete resource and scope: a static checklist keyed by product type and market, naming the frameworks it covers (CE/FCC/UKCA/CPSIA). An agent can tell this is a reference/lookup aid rather than a certification or clearance service. It does not, however, distinguish itself from adjacent siblings such as trade_compliance_pack or product_device_clearances.

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?

'Planning aid only, not certification' is a useful when-not constraint that prevents misuse as authoritative compliance evidence. Beyond that, there is no guidance on when to pick this over trade_compliance_pack or product_device_clearances, and no statement of prerequisites for the parameters (e.g., omitting markets).

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