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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is fully covered by structured data. The description usefully expands on what is computed (medians vs maximums, per-network breakdowns, filtering conditions), but says nothing about aggregation time window, data freshness, or output shape. With annotations carrying the behavioral burden, a 3 is appropriate.

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?

A single front-loaded sentence carries the metric inventory, followed by a short clause of example questions. Every element earns its place and there is no padding. The metric enumeration is dense but relevant given no output schema.

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 parameters and no output schema, the description must convey what comes back; it does so by listing the returned statistics (인상액 중앙값·최대값, 망별 최저가, 조건별 요금제 수). Read-only annotations remove the need to discuss side effects. Minor gap: no sense of scope or recency of the underlying data.

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 takes zero parameters, so the baseline is 4 — there is no argument syntax for the description to explain and nothing the schema could leave ambiguous. No parameter-level value is added or missing.

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?

Names a specific resource (알뜰폰 요금 통계) and enumerates the exact aggregate metrics it produces: 기간 할인 인상액 중앙값·최대값, 통신망별 최저가·중앙값, 조건별 요금제 수. That is far more than a restatement of the title. It stops short of 5 because it never distinguishes itself from overlapping siblings like price_index or plan_price_history, so an agent cannot rule those out from this text alone.

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?

Provides concrete trigger questions ('기간 할인 끝나면 얼마 올라?', '0원 요금제 함정', '망별 평균 요금'), which effectively tells the agent which user intents map here. It gives no exclusions and does not name the alternative statistics tools to use instead, so it stays at 4 rather than 5.

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