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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world). The description adds value beyond them: it discloses that the result includes both the daily series and a comparative 'is it cheap now' judgement, and explicitly states the tool does not forecast prices.

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 short sentences, front-loaded with the core resource before the constraints. Deducted one point because the Korean text is a full restatement of the English rather than additive information, doubling the length for no new semantics.

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 does describe the return shape (daily history plus judgement), which is a real contribution. However, for a 3-parameter tool at 33% schema coverage, the unexplained 'form' parameter and the ambiguous trip-length enum are left for the agent to guess.

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 only 33%: 'days' carries a bare default note and 'form'/'country' have no schema descriptions. The description loosely maps 'country' and 'trip length' (days) to the inputs but never explains the trip-length enumeration or what 'form' (esim vs usim) selects, so it only partially compensates for the gap.

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 and scope: 'Daily history of the cheapest unlimited eSIM price for a country and trip length, with a judgement of whether today is cheap'. This clearly separates it from the cross-country compare_countries and the current-price find_esim_prices by scope, though no sibling is named explicitly.

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 pick this over find_esim_prices or compare_countries. The one piece of guidance is a negative scope boundary ('Does not forecast'), which usefully blocks misuse for prediction but leaves the positive use case to inference.

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