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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds that the prices reflect the current moment ('지금'), implicitly contrasting with the price-history sibling, but says nothing about rate limits, ordering, or fallback when no plan matches a filter.

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?

Three short sentences, front-loaded with what is returned before the routing hint and the filter options. Nothing is padded, though the filter sentence duplicates schema-level information and the quoted phrase is slightly awkward to parse.

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 read-only, zero-required-parameter query with no output schema, the description conveys the tiered result shape and the available narrowing filters. Annotations carry the safety profile, so only the exact return structure per tier is left implicit.

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 75%, so most parameters are self-documented, and the description usefully restates that results can be narrowed by 통신망(mno), 5G(network), and 통화 무제한(voiceUnlimited). The qosMin parameter is left to the schema, which is acceptable at this coverage level but adds no depth.

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 with an explicit scope: the cheapest lifetime-discount/regular plans for each of the 1/5/10/15/30/70/100GB tiers. The phrase 'use this first for "cheapest MVNO" questions' implicitly distinguishes it from siblings like search_plans and price_index. An agent can identify what it returns without opening the 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?

Gives clear context ('알뜰폰 최저가' questions, use first) and notes the result can be narrowed by carrier network, 5G, and unlimited voice. However, it names no alternative sibling tool and states no when-not conditions, so routing is only partially resolved.

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