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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive behavior. The description adds meaningful context beyond them: weekly OFAC refresh, returned fields, x402 pricing, API-key credit cost, and a free daily allowance. It leaves some payment-flow details implicit, such as how x402 payment is performed or what happens on payment failure.

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 front-loaded with the primary use case, then coverage, return values, and cost. Despite being a single dense passage, every clause carries operational value for invoking or paying for the tool.

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 no output schema, the description supplies the key return fields: sanctioned true/false, currency, listed entity, and programme. For a read-only paid screening tool, it also covers refresh cadence and payment/free-tier mechanics, leaving no major invocation 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%, so the address and api_key parameters are already documented. The description still adds useful semantics by listing supported blockchain/currency types for the address and by explaining that api_key usage consumes credits with a free first-5-calls allowance.

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 states a specific verb and resource: screening crypto wallet addresses against the US OFAC SDN list. It names supported chains and clarifies the OFAC scope, which disambiguates it from generic EU sanctions screening siblings despite the eu_ prefix in the tool name.

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 gives clear triggers: 'Use before sending crypto to an address, or when asked if a wallet is sanctioned.' It does not explicitly name alternatives such as eu_sanctions_screen or eu_sanctions_batch, nor does it state when not to use this tool, but the wallet-specific context is sufficient.

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