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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the bar is lower. The description adds genuinely useful behavioral context the annotations lack: the index scale (world average = 100) and its directionality (higher = more expensive), which is essential to interpret the result.

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, zero filler, with the core action front-loaded and the interpretation convention immediately following. Nothing could be trimmed without losing meaning.

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 simple two-parameter, read-only tool with full schema coverage and no output schema, the description supplies the one thing structured fields don't: the index scale and direction. The only minor gap is that it doesn't clarify whether the comparison is directional (from-vs-to ratio) or symmetric.

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 100% – both 'from' (home country ISO alpha-2) and 'to' (destination ISO alpha-2) are fully documented in the schema. The description adds nothing about parameter meaning or ordering beyond restating 'two countries', so the baseline 3 applies.

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 (compare), resource (food price index) and scope (between two countries), so the agent immediately knows what it does. It does not differentiate itself from siblings like get_vanbasket (single-country lookup?) or compare_fuel_prices (the parallel fuel-index tool), leaving the choice partly to inference.

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 gives no when-to-use guidance, prerequisites, or named alternatives. With siblings such as get_vanbasket and compare_fuel_prices present, an agent gets no explicit signal about when this tool is the right pick over those.

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