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

With no annotations, the description carries the full burden and does well: it discloses that the call costs $0.003 USDC via x402 on Base, the specific data sources, and the ECB conversion basis with a returned date. It stops short of latency, freshness guarantees, rate limits, or error behavior, which keeps it below a 5.

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?

Front-loaded with the resource and computation, then default behavior, then payment terms; no filler. The single long clause chain with parentheticals is dense but every element (sources, conversion rate, default scope, price) earns its place.

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 one-parameter read tool with no output schema and no annotations, the description supplies the data provenance, default scope, conversion basis, and cost. What remains thin is the return-value shape (e.g., which fields per coin are returned beyond the rate date), but the essential call-time context is present.

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 already documents that symbols is a comma-separated ticker list with the top-20-by-Upbit-volume default. The description's 'without symbols, the top 20 Upbit markets by 24h KRW volume' largely repeats that constraint rather than adding syntax rules, casing conventions, or failure behavior. Baseline 3 applies.

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 precise resource and computation: Korea (kimchi) premium per coin from Upbit/Bithumb KRW vs Binance USDT, converted via the ECB USD/KRW rate. That is specific enough to distinguish it from siblings like prices_token_price, macro_fx, and depth_slippage without opening a 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?

The description covers the default scope when symbols are omitted (top 20 Upbit markets by 24h KRW volume), but it never says when to prefer this tool over alternatives such as prices_token_price or macro_fx, nor any exclusions. Usage is implied by the purpose rather than guided.

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