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

Annotations already indicate read-only and open-world behavior. The description adds essential operational details: the $0.002 USDC price, x402 payment method, supported chains, client libraries, and the exact return fields with their interpretations. This goes beyond what annotations provide, though it omits rate limits or error handling.

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 structured with clear sections (definition, payment, returns, args) and front-loaded with the core purpose. However, the 'South Korea ranks top 3 globally' sentence is tangential and the pricing/payment details could be moved to documentation, making it slightly more verbose than necessary.

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 doesn't need to explain return values, but it goes beyond by explaining the gap interpretation and the basis for each premium field. It also covers pricing, payment, and client compatibility, making it highly complete for a one-parameter tool. Minor gaps like rate limits do not detract significantly.

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 input schema fully documents the 'symbol' parameter with a description and default. The description adds a few more example values (SOL, DOGE) and reiterates the argument, but does not add substantial semantics beyond the schema. Baseline 3 is appropriate for 100% schema coverage.

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 uses a specific verb ('Get') and defines the resource (real-time Kimchi Premium between Upbit and Binance). It clearly explains the concept and the two premium metrics, which helps distinguish it from generic premium tools, though it does not explicitly contrast with sibling tools like get_global_vs_korea_divergence.

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 implies the tool is for real-time premium checks and provides an arbitrage use case ('Gap between the two premium values reveals real arbitrage margin'), but it does not explicitly state when to use this tool over alternatives or mention exclusions.

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