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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds material behavior beyond them: an unknown code returns found=false with risk_level unknown as a successful charged call, the price is $0.001 USDC per successful call via x402 on Base, unpaid calls yield a PaymentRequired result, and failed calls are not charged. This is exactly the billing and edge-case context an agent needs before invoking a paid tool.

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?

The description is dense but front-loaded: purpose and returned fields first, then routing guidance, then the no-data edge case, then pricing. Every sentence carries distinct, actionable information with no restatement of the title or schema.

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?

With an output schema present, return values need not be spelled out, yet the description still covers the non-obvious found=false path, the cost/charging model, and routing to the sibling tool. Nothing an agent needs to select or call this tool correctly is missing.

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% and the schema itself provides the ISO 3166-1 alpha-2 pattern plus examples, so the baseline is 3. The description adds the operational constraint that it takes one country code per call and that corridors must be checked end by end, which is meaningful semantics beyond 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?

The description names a specific verb and resource ('look up one country's anti-money-laundering risk') and enumerates the exact data returned (FATF status, Basel AML Index, CPI, EU/US designations, tax-haven flag, derived risk level). It also distinguishes itself from the sibling run_due_diligence, which handles named persons/companies, so an agent can route correctly without opening either 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?

It states concrete use cases ('assess a counterparty's country or a payment corridor') and an explicit exclusion with the alternative named ('For a named person or company use run_due_diligence, which already assesses the countries found in its hits'). It even handles the corridor edge case by telling the agent to check each end separately.

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