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

Annotations already establish the safety profile (readOnlyHint, idempotentHint, non-destructive), so the description is not burdened with that. It does add genuine behavioral context beyond the annotations: the data is refreshed daily from the official homepage and coverage begins at a 'record start date'. However, it never clarifies how far back the history goes or whether the series has gaps, which matters for a time-series tool.

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?

One compact sentence with the resource named first and the provenance/coverage caveat in a parenthetical. No filler sentences, and nothing important is buried.

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 single-parameter read tool with no output schema, the description conveys the essentials: what is returned conceptually (dated monthly prices for one plan), the data source, and the update cadence. The remaining gap is the undocumented id format, which is minor given the tool's simplicity.

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%, so the description must carry the weight. It does imply the lone 'id' parameter identifies a single plan ('요금제 하나의'), which adds real meaning over the bare string type, but it gives no format, source, or validity guidance for that identifier.

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?

The description names a specific resource and scope: the dated monthly-price record for a single plan, sourced from daily checks of the official site. An agent can tell this is a per-plan historical price series, though it does not distinguish itself from close siblings like recent_price_changes or price_index.

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?

There is no statement of when to use this tool versus the obvious alternatives (recent_price_changes, price_index, cheapest_by_data). The only implicit cue is 'one plan', which hints at single-plan lookups, but no exclusions or comparative guidance are given.

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