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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering safety. The description adds behavioral context beyond that by specifying the cost ($0.001 USDC), the x402 payment requirement, supported blockchains, and client SDKs. This is useful disclosure of operational constraints.

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 main purpose, then provides essential operational details in a structured list. The payment and docs lines are relevant and earn their place, though the emoji-heavy formatting adds minor noise.

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 simple zero-parameter tool with an output schema and read-only annotations, the description covers the core purpose, conversion use case, payment model, client options, and documentation link. It is sufficiently complete for an agent to select and invoke 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?

The tool has zero parameters, so the baseline is 4. The description adds meaning by clarifying the output is a rate for converting KRW/USD, which is helpful for understanding what the tool returns. No parameter documentation is needed.

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 starts with 'Get current USD/KRW exchange rate', which is a specific verb+resource combination. It clearly distinguishes this tool from siblings like get_kimchi_premium or get_kr_prices by focusing on the currency pair, and adds the conversion use case.

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 states 'Essential for converting between Korean Won and US Dollar prices', providing clear context for when to use the tool. However, it does not explicitly name alternatives or state when not to use it, so it misses the 'explicit exclusions' bar.

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