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

Annotations already cover the safety profile (readOnlyHint, idempotent, non-destructive), so the description's value-add is the data-provenance context: results are based on carrier official homepages, refreshed five times a day, and each result carries source citation, verification timestamp, official URL, and current fee start date. That freshness and provenance detail is genuinely useful and not present in the annotations.

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 compact sentences: purpose first, then defaults, then result contents. Well front-loaded with no filler, though the parenthetical about refresh frequency could be folded more economically.

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 13-parameter tool with no output schema, the description is close to complete: it explains the defaults, the data source and refresh cadence, and what fields accompany each result, which compensates for the absent output schema. The remaining gap is guidance on narrowing versus broadening filters and pagination behavior.

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 92%, so the schema already documents nearly every parameter, including the enum meanings and the fee/data default values. The description restates the defaults (평생 할인·정가, 월 요금 낮은 순) but adds no syntax or format detail beyond what the schema provides.

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 (find) and resource (알뜰폰 요금제 / MVNO plans) plus the mechanism (조건을 칸으로 정해 — setting conditions across fields), which separates it from the single-purpose siblings. It does not explicitly name a sibling to contrast with, so differentiation is implicit rather than stated.

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 multi-condition filtering is this tool's role, which distinguishes it from cheapest_by_data and price_index, but it never says when to prefer it or when not to. No prerequisites or exclusions are given, leaving the routing decision largely to inference from the sibling names.

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