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

Annotations already supply readOnlyHint=true and openWorldHint=true, so the bar is lower. The description adds a genuine behavioral constraint not in the structured fields — 'Observed registered trades only' scopes the data — plus pricing and payment mechanics ($0.005 USDC per call via x402 on Base), which the agent needs to know before invoking.

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?

Two dense sentences with the purpose front-loaded ahead of the scope caveat and the pricing. No filler, and the ordering puts the most decision-relevant content first.

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 usefully names the returned aggregations (trades, median price, price per m2, grouped by district/month/complex) plus the scope and cost caveats. It is largely complete for a read-only query tool; the residual gap is the undocumented parameter semantics, which is scored separately.

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 description coverage is 0% across 5 parameters, so the description must carry the load. It loosely maps 'by district, month and complex' onto region/month/apt, but leaves the difference between month (string) and months (integer) and the role of the required 'question' parameter unexplained, so the ambiguity between the two month parameters is unresolved.

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+resource: Korean apartment sale prices from the MOLIT real-transaction register, and enumerates the outputs (trades, median price, price per m2). It does not, however, distinguish itself from the sibling kr_apartment_trend, which is the obvious near-neighbor an agent must choose between.

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?

Usage is implied by the domain (you call it when you need apartment sale-price data from a Korean or English question), and the cost line hints at a decision factor. But there is no explicit when-to-use/when-not and no mention of the alternative kr_apartment_trend for trend-style requests.

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