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

Annotations already mark this as read-only and open-world, but the description adds substantial behavior beyond them: supported chains, output fields (sanction status, list name, SDN program, source link), the explicit caveat that it never declares an address clean, the informational-only disclaimer, the $0.003 USDC price via x402, and that failed calls are not charged.

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 core action and coverage, then layers in output details, caveats, and pricing without wasted words. Each clause contributes useful information for selecting and invoking 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 an output schema present, the description need not explain return values, but it still names the reported fields. Combined with chain coverage, caveats, pricing, and payment details, an agent has everything needed to call the tool correctly.

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 single parameter already documents the comma-separated format and maximum of 20 addresses. The description reinforces the 20-address limit but adds no new syntax or meaning beyond what the schema provides, so the baseline of 3 is appropriate.

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 ('Screens') and resource ('crypto addresses') against a precisely named list (US Treasury OFAC SDN digital currency address list). It also names supported chains and the number of currencies, which clearly distinguishes it from siblings like sanctions, evm_address, or btc_address.

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?

The description makes the screening context clear: use it to check up to 20 crypto addresses for OFAC SDN sanction status. It does not explicitly name alternative tools such as sanctions or screen_debarment, so it falls short of full when/when-not guidance, but the intended usage is unambiguous.

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